When to Go to the Hospital for a UC Flare

The threshold that hospital teams actually use is around six or more bloody stools in 24 hours plus at least one systemic sign: a temperature above 37.8C, a resting pulse over 90, a haemoglobin below 10.5 g/dL, or raised inflammatory markers. An attack that meets that is called acute severe ulcerative colitis, and a 2025 review describes it plainly as a medical emergency requiring hospitalisation, affecting up to a quarter of people with ulcerative colitis (Jamal 2025).

Here is the problem with handing you that list and walking away. Two of those markers are blood tests. You cannot check your haemoglobin, your ESR or your CRP from your bathroom. So the criteria that decide whether you get admitted contain two items you have no way of measuring, which means the honest home version of the question is different from the textbook version.

This guide gives you the home version. What you can count, what you can measure with a thermometer and two fingers on your wrist, which signs skip the counting entirely, what an emergency department can and cannot do for a colitis flare, what an admission actually consists of, and the numbers to walk in holding. It also prints the places where the published arithmetic does not add up, because several of the figures that get quoted at you are shakier than they look.

The short answer, in numbers you can actually check

Work through these four in order. The first three you can do yourself in about two minutes.

These are the Truelove and Witts criteria, which originate in a 1955 British Medical Journal trial of cortisone in ulcerative colitis (Truelove 1955). We should be straight about one limit on that citation: the 1955 paper has no abstract indexed and its full text would not load for us through any of the three routes we tried this run, so we cite it for where the classification comes from, not for its wording.

For the wording we used two sources we could read in full, and they do not agree exactly. A 2025 peer-reviewed review of acute severe colitis, which declares no external funding and no conflicts of interest, defines it as more than six bloody bowel movements a day together with at least one of: fever above 37.8C, tachycardia above 90 bpm, haemoglobin below 10.5 g/dL, or raised inflammatory markers, given as ESR above 30 mm/h or CRP above 30 mg/L (Jamal 2025). A review of hospital management renders the same criteria as six or more bloody bowel movements a day with one marker of systemic toxicity, and lists ESR rather than CRP (Feuerstein 2021).

So one source says six and the other says more than six, and they differ on whether CRP substitutes for ESR. We are not going to pick. The disagreement is itself the point: if two careful sources cannot agree on whether the cutoff is six or seven, then a stool count of exactly six was never going to be the thing that decides your evening. The systemic signs are.

Those criteria still sit underneath current guidance on ulcerative colitis in adults, published by the American College of Gastroenterology (Rubin 2025), the European Crohn's and Colitis Organisation (Raine 2022) and the British Society of Gastroenterology, whose 2025 guidelines state they were produced without external commercial funding and with contributors supported through their public-sector and NHS roles (Moran 2025). We cite those three for being the current guidance on this condition. We could read only their abstracts, none of which reproduces the severity criteria, so we are not quoting anything from inside them.

Both halves matter. Six bloody stools a day with a pulse of 72 and no fever is a bad flare that needs your IBD team within days, not an emergency department tonight. Four bloody stools a day with a pulse of 118, a temperature of 38.2C and dizziness when you stand up is a same-day assessment, even though the count is under six. The count on its own has never been the decision.

One step further up the same scale is fulminant colitis, described in the same 2025 review as stool frequency above ten a day with continuous rectal bleeding, abdominal pain, radiographic evidence of colonic dilatation and systemic toxicity. Initial treatment is similar, but the risk of toxic megacolon and perforation is substantially higher, and surgeons get involved earlier (Jamal 2025).

Why this is not a rare or dramatic scenario

A quarter of people with ulcerative colitis will have at least one admission for a severe attack. In a systematic review of everyone diagnosed with ulcerative colitis in Oxford, 750 patients met inclusion criteria out of a cohort of 1,853, and 24.8%, that is 186 of 750, had at least one admission for acute severe colitis, across 294 admissions (Dinesen 2010).

That figure matters for a specific reason. Almost everyone who posts the "am I overreacting" question assumes they are the exception. On the numbers, roughly one person in four with this diagnosis goes through it. A thread in r/UlcerativeColitis titled simply "How do I know I need to go Hospital?" describes exactly the shape of it: months of flaring, prednisolone that has not helped much, four to six bowel movements a day with blood and mucus, constant tenesmus, looking outwardly fine, and a specific fear of turning up and being sent home (r/UlcerativeColitis thread). The most upvoted reply was the plainest one: if you are unwell enough to be considering it, go.

We are not going to rebuild the timeline of what happens after admission here. Our guide to how long a UC flare lasts covers the day-three clock, the colectomy trajectory across repeated admissions and why guessing at durations in a severe attack is actively unhelpful. This article is about the decision you make before any of that.

The go-now list: the signs that skip the count entirely

Some things do not wait for a stool count, a phone call or a Monday morning. Treat any of these as a reason to seek emergency assessment the same hour.

The reason the swollen abdomen sits at the top of that list is toxic megacolon: the colon dilating under severe inflammation, which can progress to perforation. A hospital medicine case report of perforated toxic megacolon in a woman with newly diagnosed ulcerative colitis refractory to steroids and biologic therapy describes the typical presentation as abdominal distension, severe pain, fever and signs of systemic toxicity, and stresses that early recognition is what reduces the harm (Dao 2024).

The definition clinicians use, the Jalan criteria, pairs radiographic colonic dilatation with systemic toxicity. A 2026 case report is instructive precisely because its patient did not meet them: an 83 year old woman with long-standing pancolitis had transverse colon dilatation progressing from roughly 70 mm to 95 mm on serial X rays despite high-dose steroids and infliximab, but she lacked high fever, marked tachycardia and leucocytosis, so she did not meet the criteria for toxic megacolon. Surgery was chosen anyway, on the radiographs, and the removed segment showed broad disruption of the muscle layer (Uchino 2026).

The practical lesson for you is not the criteria. It is that a distending abdomen can be structurally serious before it looks toxic on paper, which is why "my abdomen is swelling and it hurts" is a go-in symptom rather than a wait-and-score symptom.

The blood clot risk, and the statistic that gets quoted backwards

This is the part of the decision that almost no patient-facing page handles, and it is handled wrongly when it appears at all.

A UK cohort study followed 13,756 people with inflammatory bowel disease against 71,672 matched controls. Overall, people with IBD had a higher risk of venous thromboembolism, with a hazard ratio of 3.4 (95% CI 2.7 to 4.3) and an absolute risk of 2.6 events per 1,000 person-years. At the time of a flare, the hazard ratio rose to 8.4 (5.5 to 12.8), with an absolute risk of 9.0 per 1,000 person-years. Then the study split flares by whether the person was in hospital. The relative risk was much higher during non-hospitalised flares, at 15.8 (9.8 to 25.5), than during hospitalised ones, at 3.2 (1.7 to 6.3) (Grainge 2010).

Read only that far and you would conclude that a flare at home carries about five times the clot risk of a flare in hospital. The absolute numbers in the same sentence say the opposite. The absolute risk during a non-hospitalised flare was 6.4 per 1,000 person-years. During a hospitalised flare it was 37.5 per 1,000 person-years, roughly six times higher.

A later study from the same group, funded by the patient charity Crohn's and Colitis UK, sharpened it further. Among ambulatory patients, the clot risk was raised during both acute and chronic disease activity, with hazard ratios around 3.94 and 3.97, but the absolute risk stayed below 5 per 1,000 person-years. For inpatients not undergoing major surgery the hazard ratio was 1.13 (0.63 to 2.02), a confidence interval that crosses no effect, against 2.43 (1.20 to 4.92) for surgical patients, with absolute risks of 31.1 and 59.5 per 1,000 person-years respectively, and risk still elevated for six weeks after discharge (Chu 2018).

What you should take from this is narrow and useful:

1. A flare, at home, raises your clot risk above your own baseline. New calf pain and swelling, or new breathlessness or chest pain, is a go-in symptom and not a muscle strain to walk off.
2. Admission does not remove the risk, it manages it. Clot prevention injections are routine in acute severe colitis because it is a high-clotting state (Feuerstein 2021).
3. If you are offered those injections as an inpatient, they are not optional extras. Feuerstein notes that they are sometimes ordered and then declined, and describes reminding patients daily why they matter.

Can you score yourself? The one index that needs no blood test

Almost every severity index in ulcerative colitis wants a laboratory value. The exception is the Pediatric Ulcerative Colitis Activity Index, which despite the name is built entirely from things a person can report: abdominal pain, rectal bleeding, stool consistency, number of stools in 24 hours, whether stools wake you at night, and activity level.

Its feasibility is documented. Across a real-life registry, 97.6% of 770 eligible visits had a completed score, against only 47.6% for the contemporaneously collected Crohn's disease index in the same database, and scores were markedly higher in patients who went on to need treatment escalation, a median of 45 points against 0 (Turner 2009).

And it works in adults. A multicentre retrospective cohort of 153 adults with acute severe colitis found the index strongly predictive of intravenous steroid failure. Of those 153 patients, 51 (33%) needed second-line therapy and 23 (15%) had a colectomy by discharge. Median scores at day three were 55 in non-responders against 38 in responders, and at day five 55 against 20. The authors propose a score of 45 or more on day three as a trigger to prepare for second-line therapy, and 65 or more on day five as a trigger to start it (Atia 2021).

Two honest caveats before you go and score yourself.

First, the index was validated in hospital, on day three of intravenous steroids, as a tool for deciding whether to escalate treatment. It was not built or tested as a home triage tool, and nobody has shown that a home score predicts who should present. Using it as a shared vocabulary with your team is reasonable. Using it as permission to stay home is not.

Second, the paper's own abstract describes a score of 45 or more on day three as having "an excellent negative predictive value" for steroid failure, which reads oddly, because a high score signalling failure would be a matter of positive predictive value. The sense that fits the data is that scoring below 45 makes failure unlikely. We are noting the phrasing rather than resolving it, because the abstract does not give the numbers to settle it.

For a self-scoring instrument actually designed for use outside hospital, our guide to knowing whether your ulcerative colitis is flaring walks through the SCCAI and how to build a personal baseline, which is the measurement that makes "six stools a day" mean something specific rather than generic.

"Will the ER actually do anything?" Here is the study that measured it

This is the question the threads ask most often, usually with resignation. One post asked directly whether it was worth going to an emergency department or whether they would just be kicked out, describing 16 bowel movements a day with blood, being unable to drink water without bleeding, new anaemia, and a 15 hour road trip they still had to make for work (r/UlcerativeColitis thread). The replies ranged from "they can give you IV fluids but not something magic to stop your flare" to one person's account of two local emergency visits that ended in "come back if it gets worse" before a larger hospital admitted them. The original poster later came back to say they had gone, were found to have a partial blockage and a Clostridioides difficile infection, and were admitted.

There is a study that gets at what the emergency department is actually measuring. Researchers looked at 164 admissions for an IBD flare across two urban academic centres, all tested for C. difficile, and asked which findings at presentation predicted a "complex hospitalization", defined as a stay longer than seven days, an inpatient colectomy, or inpatient infliximab or ciclosporine. Of the 164, 56 (34%) were complex. The predictors were tachycardia at triage, hypotension at triage, a low albumin at presentation, C. difficile infection, and endoscopic colitis. A two-item score built from heart rate and albumin gave an area under the curve of 0.744. Most usefully, 44 of 48 patients (91.7%) with a score of zero, meaning a heart rate under 99 and an albumin of 3.4 g/dL or above, had a non-complex hospitalisation. The work was supported by a Crohn's and Colitis Foundation grant and a National Institute of Diabetes and Digestive and Kidney Diseases career development award, and no conflict of interest statement appears in the PubMed record, so we cannot confirm one way or the other whether the authors declared any (Verma 2022).

Translate that into your evening. The things the emergency department checks in the first fifteen minutes, your heart rate and blood pressure at triage and your albumin on the first blood draw, are close to the whole of the early prognosis. If those come back normal, the statistical expectation is that you are not in the group heading for rescue therapy or surgery on this admission. Which means being given fluids and a referral is frequently the medically correct outcome rather than a dismissal, however it feels in the corridor at 2am.

For contrast, here is a properly constructed one from the same field. A Scottish cohort of 39 patients given infliximab as rescue therapy for acute severe colitis found albumin a consistent predictor of non-response, with an odds ratio of 12.0 (95% CI 1.28 to 112.7). The geometric mean of 1.28 and 112.7 is 12.0, exactly the point estimate, which is what a correctly log-symmetric interval looks like. That study also reported two serious adverse events including a death from pneumonia, and concluded that those risks should be discussed with patients beforehand (Lees 2007).

What an admission actually consists of

People delay partly because they do not know what they are agreeing to. Here is the shape of it, taken from a review of hospital management of acute severe ulcerative colitis, with the studies behind individual steps cited separately.

That whole sequence is described in (Feuerstein 2021), an expert interview rather than a guideline or a trial, and its author declared no relevant conflicts of interest. Treat it as how one experienced clinician describes standard practice, not as a protocol you can hold anyone to.

It is worth knowing how much practice varies, because the table above is the ideal rather than a guarantee. A survey of 228 gastroenterologists across India found that the Truelove and Witts criteria were the most commonly used for diagnosis, by 74.1%, and the Oxford criteria the most common way to assess steroid response, by 65.8%. But biopsies for cytomegalovirus during the first sigmoidoscopy were taken by only 32.9%, and low molecular weight heparin for clot prevention was never prescribed by 27.2% of respondents (Bhardwaj 2026). That is a self-reported survey in one country and it does not describe practice where you live. It does tell you that the clot prevention injection is worth asking about rather than assuming.

On that point, one common worry is worth answering directly. People bleeding heavily are often alarmed at being offered a blood thinner. The 2025 review states that rectal bleeding in acute severe colitis is not considered a contraindication to clot prophylaxis unless it is life-threatening, while noting that the optimal type, dose and duration of anticoagulation remain unsettled (Jamal 2025). If you are worried about it, ask your team to explain the balance for you specifically rather than declining it quietly.

Three of those steps deserve their own note.

The stool test happens even if you have had no antibiotics. C. difficile infection in IBD rose sharply over the 2000s, from 1.8% of IBD patients in 2004 to 4.6% in 2005 in one referral centre, and it worsens outcomes (Issa 2007). A review of the problem makes the point that matters for you: the clinical presentation of C. difficile and of a flare are so similar that prompt testing is essential, because escalating immunosuppression while an untreated infection runs is the bad outcome, and the classical risk factors such as recent antibiotics or visible pseudomembranes are often absent in IBD patients who have it, so their absence should not be treated as reassurance (Ananthakrishnan 2010). The same problem in Crohn's disease, telling a flare apart from a gut infection, is worked through in our guide to how to tell if you are in a Crohn's flare, and the reasoning about infection transfers even though the disease does not.

The biopsies are partly looking for a virus. A national inpatient analysis found 145 hospitalised ulcerative colitis patients with cytomegalovirus infection had a much longer length of stay, 16.31 days against 5.52, and higher charges, but not more surgery or higher mortality than ulcerative colitis patients without it (Grossberg 2018). That is a more reassuring finding than the length-of-stay number sounds.

The scope tends to happen early, and the evidence for that is suggestive rather than settled. A single-centre retrospective study of 112 patients hospitalised with acute severe colitis compared sigmoidoscopy within 72 hours against later. The early group had fewer days of intravenous steroids, 4.5 against 9.2. Colectomy rates were 17% against 28%, but that comparison was not statistically significant, at p = 0.23. A separate continuous analysis reported that longer time to sigmoidoscopy carried a 16% increased risk of colectomy, with a hazard ratio of 1.16 and p = 0.002 (Sharma 2023). Two cautions. The abstract does not state the unit of time that hazard ratio applies to, and a hazard ratio of 1.16 means nothing without knowing whether it is per day or per something else. And in a retrospective single-centre cohort, the timing of a scope is not random: how sick someone looks influences how fast they get scoped, in both directions. The direction of travel is plausible, the size of the effect is not established.

The mistakes that make a flare worse while you wait

Antimotility drugs during a severe flare. Loperamide is the one that comes up constantly in the threads, usually as a way to get through a shift or a journey. Toxic megacolon associated with loperamide therapy was reported in JAMA in 1979 (Brown 1979). That is a single case report and we could find no abstract for it, so we cite it for existing rather than for its detail. The concern is older still: a 1963 Canadian Medical Association Journal case report of toxic dilatation during an acute relapse of ulcerative colitis already stated that the use of opiates and anticholinergic agents had been suggested as a contributing factor and that these agents should be avoided in the acute stage (Glay 1963). One case report from 1963 is not strong evidence of anything. But the underlying logic holds regardless: slowing the bowel does not reduce inflammation, it reduces the number you would have counted, and that number is the signal your team is using.

Opioids for the pain. A retrospective cohort in English primary care covering 3,517 people with Crohn's disease and 5,349 with ulcerative colitis found opiate prescribing rose from 10% of subjects in 1990 to 1993 to 30% in 2010 to 2013, and that heavy use of strong opiates was significantly associated with increased premature all-cause mortality, with heavy use of any opiate or of codeine alone also associated with premature death in ulcerative colitis. Tramadol alone or with codeine was not (Burr 2018). This is an observational association, and people prescribed heavy opioids differ in many ways from those who are not, so it does not prove the drugs caused the deaths. The study was supported by the National Institute for Health Research and Crohn's and Colitis UK. Alongside it, Feuerstein's practice account is that patients with acute severe colitis should not have standing opioid orders at all, and that non-opioid analgesia should be used where possible.

Oral iron in the middle of a bad flare. This one comes up repeatedly, including one account of hydrocortisone enemas cutting bathroom trips from 16 a day to five, then a single oral iron tablet apparently undoing the progress (r/UlcerativeColitis thread). That is one person's experience and not evidence that iron worsens colitis. It is a legitimate thing to ask your team about, because the timing and route of iron replacement during active disease is a clinical decision with alternatives, and it is not a reason to abandon treating anaemia.

Waiting because your abdomen "feels like it always does". The hardest version of the delay is the person who is systemically unwell without noticing. One account in r/UlcerativeColitis describes three weeks of fever dismissed as a preschool bug, fatigue that reduced their day to moving from bed to sofa, then arriving at hospital with a resting heart rate above 160 and a blood pressure low enough that staff were surprised they had walked in. The diagnosis was cytomegalovirus colitis with a concurrent C. difficile infection, and the admission ran three weeks (r/UlcerativeColitis thread). You do not need to match that story to justify going in. But it is why the pulse matters more than how the pain compares with last time.

The numbers to walk in holding

The single highest-value thing you can do before a hospital visit is to arrive with the measurements someone would otherwise have to reconstruct from your memory while you are exhausted and needing the toilet.

Write these on one side of paper, or have them on your phone:

1. Daily bloody stool count for the last seven days. Numbers, one per day. Not "loads".
2. Blood present each day, and whether it changed character: streaking against clots, fresh red against darker.
3. Night-time stools, because getting up at night is one of the items that separates a bad patch from a severe one.
4. Resting pulse, taken sitting still for five minutes first, and your temperature.
5. Weight now against your usual weight.
6. Fluids in over the last 24 hours, roughly, and whether you have kept them down.
7. Every current medicine with dose and start date, including suppositories and enemas.
8. The date your last steroid course started and ended.
9. Your most recent CRP, calprotectin or haemoglobin result, if you have it.
10. Your IBD team's name and contact details, and when you last saw them.

There is a reason to make it a single page rather than an export. Our guide to building a symptom record a clinician will actually read covers what survives a ten-minute slot and what gets ignored, and the answer is consistently the short version.

If you already log your days, you already have items one to three. If you do not, Clairop records daily symptom entries and turns a run of them into a report you can bring to an appointment, which is the format that fits this job. You can see how the tracking and reporting side works on our how it works page.

Would a home calprotectin test settle it? No, and here is why

People increasingly own home calprotectin kits, and the temptation is to test before deciding. The evidence says that will not answer this question.

In 90 patients admitted with acute severe colitis requiring intensive inpatient treatment, faecal calprotectin was enormously raised across the group, with a median of 1,020 micrograms per gram and an interquartile range of 601.5 to 1,617.5. Of the 90, 31 (34.4%) needed a colectomy. Calprotectin was higher in those who did, 1,200 against 887, but only just, at p = 0.04. The area under the curve for predicting colectomy was 0.65. At the best cutoff of 1,922.5 micrograms per gram, specificity was 97.4% but sensitivity was only 24.0% (Ho 2009).

Work through what that sensitivity means for you. At that cutoff, roughly three out of every four people who went on to need a colectomy had a calprotectin below it. A result under 1,922 would have offered them false reassurance on the very night it mattered. The likelihood ratio of 9.23 the paper reports is internally consistent with those figures, 0.24 divided by 0.026, so this is not a paper with an arithmetic problem. It is a paper whose honest conclusion is that calprotectin is a poor discriminator in this specific decision.

Calprotectin has real uses: confirming that symptoms come with inflammation, tracking a trend over weeks, and settling whether a bad patch is inflammatory at all. Our guide to what calprotectin levels mean in ulcerative colitis covers assay differences, day-to-day variation and why one sample is a noisy sample. None of that makes it a triage test, and waiting for a home result should never delay an assessment you already think you need.

How low does haemoglobin have to be? Two different jobs for one number

Threads are full of people discovering at the hospital that their haemoglobin was 7 or 8, and of people confused that nobody transfused them at a number that sounded alarming. Both reactions come from conflating two separate uses of the same measurement.

As a severity marker, a haemoglobin below 10.5 g/dL is one of the systemic signs that, alongside around six or more bloody stools a day, makes an attack severe (Feuerstein 2021). That is a threshold for classifying how ill you are.

As a transfusion trigger, the number is much lower. The 2023 AABB international guidelines, drawing on 45 randomised trials in 20,599 adults comparing restrictive thresholds of typically 7 to 8 g/dL against liberal thresholds of 9 to 10, recommend for haemodynamically stable hospitalised adults a restrictive strategy, considering transfusion when haemoglobin falls below 7 g/dL, with 8 g/dL reasonable for people with pre-existing cardiovascular disease. They also state explicitly that clinical context and alternatives to transfusion should shape the decision for an individual (Carson 2023).

Two caveats we should name rather than bury. Those 45 trials were not conducted in acute severe colitis, so this is general hospital practice applied to your situation rather than colitis-specific evidence. And the recommendation is explicitly for haemodynamically stable patients, which is precisely the condition that stops applying if you are tachycardic and hypotensive from ongoing bleeding.

So a haemoglobin of 8.2 can simultaneously mean your flare is classified as severe and that transfusion is not indicated. Those are not contradictory answers. They are answers to different questions.

A worked example: two people, the same Saturday night

Both have had ulcerative colitis for six years. Both are having the worst week in two years. Both are deciding at 9pm on a Saturday.

Person A. Nine bloody stools yesterday, eleven today, up from a usual two. Blood at every one. Got up three times last night. Temperature 38.1C. Resting pulse, counted properly sitting down, 112. Felt greyish standing up from the sofa twice. Has managed about half a litre of fluid all day. Abdomen sore but not swollen.

Person A meets the severity threshold twice over: the count is above six and climbing, and there are two systemic signs. The near-faints and the fluid intake move it from "same day" to "now". Person A should go to an emergency department tonight, or call the emergency number their IBD team gave them if that route is faster where they live. On the emergency department presentation score, a heart rate of 112 already puts them out of the low-risk group before anyone has drawn blood (Verma 2022).

Person B. Six bloody stools yesterday, six today, up from a usual one. Blood is streaking, the same as previous flares. No night-time stools. Temperature 36.9C. Resting pulse 76. No dizziness. Eating and drinking normally. Weight unchanged.

Person B has a genuine flare that needs treatment stepped up, and it needs a clinician this week, not this month. But with normal observations, normal fluid intake and no night-time symptoms, the emergency department on a Saturday night is most likely to produce a long wait, a normal set of bloods and a referral. The better move is to contact the IBD team or advice line first thing Monday, or an out-of-hours GP service now if the count keeps climbing, and to start counting properly tonight so Monday's conversation has numbers in it.

The difference between A and B is not how much either is suffering. It is the presence of systemic signs. That is uncomfortable, because suffering is what you feel and systemic signs are what gets acted on. It is also why writing down the pulse and the temperature is worth doing even on the nights you decide to stay home: it converts your judgement into something transferable.

Should you call your IBD team first, or just go?

Call first if you can reach a human the same day. Go without calling if you cannot, or if anything on the go-now list applies.

An IBD team or specialist nurse advice line can do things an emergency department cannot: order urgent bloods and a stool sample without a wait, bring forward a clinic slot, arrange a direct admission that skips triage entirely, and know your history. They can also tell you that what you are describing does not need tonight, which is worth something.

What to say, in about thirty seconds, because advice lines are busy:

"I have ulcerative colitis, diagnosed 2019, currently on [medicine and dose]. Over the last four days my bloody stools have gone from two a day to nine, with blood every time. I am getting up twice a night. My temperature is 38.1 and my resting pulse is 112. I have kept fluids down but not much. I am asking whether I need to be seen today."

That gives them the classification markers, the trend and the specific question, in that order.

One honesty point. We could find no trial testing whether calling an advice line first, rather than presenting directly, changes outcomes, and that reflects our searching of PubMed and Europe PMC rather than proof that none exists. The nearest evidence is a retrospective study in which IBD patients managed through structured care pathways had fewer emergency department visits than those who were not, a difference of 30.7 visits per 100 patients at 12 months. It was funded by Crohn's and Colitis Canada and a centre-of-excellence programme (Lytvyak 2020). That supports organised routes into care being better than unorganised ones. It does not tell you what to do tonight.

If the problem is that you cannot get your team to take the flare seriously at all, that is a different and structural problem, and our guide to what to ask a gastroenterologist about colitis covers the questions that tend to move a consultation forward.

When it is not your colitis

Not everything that happens during a flare is the flare, and two patterns deserve specific attention.

New pain in one place, different in character. A post in r/UlcerativeColitis described two years of anaemia that dived again after every iron infusion, blamed on heavy periods, then intermittent back and abdominal pain and blood in the stool, then a CT reported as acute colitis with an 8 by 8 cm abscess, which an emergency colonoscopy showed was bowel cancer (r/UlcerativeColitis thread). Several replies pointed out, fairly, that this was a story about acute colitis and a missed cancer rather than about ulcerative colitis, and that people with ulcerative colitis have more colonoscopies than almost anyone. Both things are true. The transferable lesson is not "your flare might be cancer". It is that anaemia which will not hold after repeated iron replacement, and localised pain that does not fit your usual pattern, are reasons to ask for imaging rather than another escalation of colitis treatment.

Kidneys and dehydration. A meta-analysis of 17 retrospective cohorts covering 20,127,976 patients, of whom 140,482 had IBD, found IBD associated with increased odds of acute kidney injury, with a pooled odds ratio of 1.87 (1.53 to 2.29). Read the subgroups before you apply it to yourself: the association was most prominent in surgical patients, at 2.17, including orthopaedic at 2.22 and spinal at 2.15, while associations in the infection and acute coronary syndrome subgroups were less consistent, and risk of bias was judged moderate (Nguyen 2026). That is not a study about people admitted with a colitis flare, and it would be wrong of us to present it as one. It is a reason to take fluid intake seriously and to expect your kidney function to be checked, nothing more specific than that.

Myths worth dismantling

"They will just send me home, so there is no point going." Sometimes they will, and sometimes that is correct. But the visit is not wasted: a set of bloods, a stool sample and a documented set of observations are exactly what your IBD team needs to escalate treatment, and they are hard to obtain any other way at a weekend. What one thread described as the emergency department being "a stop gap not a solution" is accurate and also not an argument against using a stop gap (r/UlcerativeColitis thread).

"It does not count until I am at ten or more a day." The threshold is six with a systemic sign, not ten. And a count that has doubled in four days is more informative than a count that has been high and stable for a fortnight. Note also that one reply in the very first thread we read said that four to six times a day with some blood "isn't the end of the world". For some people, at some times, that is true. It is also two stools short of the classification threshold, and it says nothing at all about pulse, temperature or haemoglobin, which is where the actual decision lives.

"Bleeding is normal for me, so bleeding does not count." Habituation is the biggest single risk here. What counts is change: blood at every stool where it used to be occasional, clots rather than streaks, or darker blood rather than fresh. One reply in a "when to go to hospital" thread made the point that pain should not be dismissed and that darker blood is a particular concern (r/UlcerativeColitis thread). That is community advice rather than evidence, but the underlying principle, report a change in character rather than a level you have grown used to, is sound and costs nothing.

"Intravenous steroids are just prednisolone in a drip." Feuerstein makes an interesting observation here: roughly two thirds of patients respond to intravenous corticosteroids regardless of what they were on before, including people who had already failed oral steroids, which he calls surprising given that oral and intravenous steroids are comparably bioavailable (Feuerstein 2021). We flag that as one clinician's account of observed practice rather than as a trial finding, because it is. Either way, the reason admission differs from taking tablets at home is not only the route: it is the monitoring, the day-three decision point, the infection testing, the clot prevention and the ability to escalate within hours.

"A really high calprotectin means go in." Covered above. In acute severe colitis it was raised in essentially everyone and its area under the curve for predicting colectomy was 0.65 (Ho 2009).

"If I go in, they will take my colon out." The direction of travel over the last two decades is the other way. Among 10,051 people aged 18 to 60 in England with a first emergency admission for ulcerative colitis between 2007 and 2017, mortality was 0.2% in hospital and 0.5% at 12 months. Comparing 2007 to 2011 with 2012 to 2017, the colectomy rate fell during acute admissions, with an odds ratio of 0.85 (0.72 to 0.99, p = 0.038), and at 12 months, 0.73 (0.61 to 0.87) (King 2020).

Two things to hold alongside that. First, the study reported that people who received anti-TNF therapy during the admission had a 70% increased risk of colectomy during that admission, an odds ratio of 1.72 (1.29 to 2.31). That almost certainly reflects confounding by indication: the people given rescue therapy were the sicker ones. The abstract also describes odds ratios as "risks" throughout, which is a common conflation worth noticing when you read a number like this. Second, this study lists funding from Merck Sharp and Dohme, a pharmaceutical company, which is worth knowing when reading a paper that reports a fourfold increase in anti-TNF use over the study period.

On the older baseline, a systematic review and meta-regression of 32 studies pooled 1,991 patients with severe ulcerative colitis, of whom 581 required a colectomy. The authors report that as a weighted mean of 27% (95% CI 26% to 28%), and 22 deaths, about 1%. We would note that the crude proportion, 581 divided by 1,991, is 29.2% rather than 27%, and the difference is the weighting across studies of different sizes. The paper's headline finding was that the colectomy rate had not changed over the preceding 30 years, and that they could find no support for methylprednisolone doses above 60 mg a day (Turner 2007).

"Asking about hospital makes me a difficult patient." Worth naming, because it drives real delay. A thread venting about a first emergency visit describes a doctor making a crude joke outside the door, a rectal examination the patient cried through, being sent home with an enema and a laxative on a working diagnosis of constipation, and later discovering that the inflammatory markers from that visit had been markedly raised (r/UlcerativeColitis thread). That is a bad experience, and it is not evidence about how you will be treated. It is a reason to walk in with numbers rather than adjectives, because numbers are much harder to reinterpret as anxiety.

What happens after: the part that reduces the next visit

Readmission is common and the things that predict it are not the ones you would guess. A retrospective analysis at a tertiary centre found 356 patients admitted at least once over two years for an unplanned IBD-related reason: 48.9% once, 38.2% two to four times, and 12.9% five or more times. After excluding 33 people with an admission in the 90 days before the index one, 102 patients were readmitted within 90 days. The final model retained depression (hazard ratio 1.99, 1.33 to 3.00) and chronic pain (1.88, 1.14 to 3.10). Steroid use in the previous six months gave 1.33 (0.92 to 2.04), a confidence interval that crosses no effect, and the authors correctly conclude that disease activity, as they proxied it, was not related to readmission (Allegretti 2015).

Two caveats before anyone over-reads that. Steroid prescriptions in the previous six months are a crude stand-in for disease activity, so "disease activity did not predict readmission" is a statement about that proxy rather than about inflammation. And depression and chronic pain being the surviving predictors in a retrospective single-centre model is a hypothesis worth taking seriously, not a settled causal finding. What it does suggest is that the mental health and pain side of this is not an optional add-on to flare management, and it is a reasonable thing to raise at the discharge conversation rather than at the next crisis.

For what follows a severe attack medically, including the rescue therapy evidence, the sibling guide to how long a UC flare lasts covers the trial that compared ciclosporin against infliximab in steroid-refractory acute severe colitis and found neither better than the other (Laharie 2012), along with the day-three and day-seven decision points.

A number we could not reconcile

Two, in fact, and they are worth printing.

First. The Oxford acute severe colitis study reports in its results that 24.8% of 750 patients had at least one admission, and that colectomy occurred in 39.8% (74 of 186) of those with such an admission against 12% (93 of 750) overall. All of that reconciles: 186 divided by 750 is 24.8%, 74 divided by 186 is 39.8%, 93 divided by 750 is 12.4%. But the abstract's conclusion then says "20% come to colectomy on first admission, but 40% after two admissions", and we have seen the paper's per-admission figures quoted elsewhere as 19.9% after one episode, 29.0% after two and 38.2% after three. Those two statements cannot both describe the same quantity. The likeliest benign explanation is that the conclusion's "40%" is a rounding of the 39.8% figure for anyone who ever had such an admission, rather than a two-admission-specific number. We could not settle it, because the full text of that paper would not load for us this run (Dinesen 2010). If you see "40% after two admissions" quoted at you, treat it with caution.

Second. A single-centre series of 489 ulcerative colitis patients identified 112 presenting with acute severe colitis, of whom 42% had an incomplete or absent response to intravenous steroids, 28.6% received rescue therapy, and 26.8% required surgery. The rescue therapy breakdown is given as 22 with infliximab, 10 with ciclosporin and 1 with sequential treatment. That sums to 33 people, which is 29.5% of 112, while 28.6% of 112 is 32 people. If the sequentially treated patient is counted inside both the 22 and the 10, the distinct total is 31, which is 27.7%. Neither reading gives 28.6%. It is an off-by-one somewhere, it does not change the paper's message, and the finding itself, that the Lindgren score outperformed the Mayo, Oxford and Edinburgh scores for predicting steroid failure, need for rescue therapy and surgery, stands on its own areas under the curve (Bernardo 2019).

We print these not to score points. If a page quotes these studies at you with a confident single number and no arithmetic, it has not checked.

The severity scores your team will use, briefly

You do not need to know these, but recognising the names helps you follow what is being decided around you.

• Oxford, or Travis, index. On day three of intravenous steroids, more than eight stools that day, or three to eight stools together with a CRP above 45 mg/L, identifies most of the people who will need a colectomy on that admission. It came from 51 consecutive episodes of severe colitis in 49 patients in Oxford (Travis 1996).
• Lindgren, or Swedish, index. Stools per day plus 0.14 times CRP in mg/L, with a score of 8 or more reported as predicting a colectomy rate of 72%, a formula we took from (Feuerstein 2021) rather than from the original paper's abstract, which does not spell it out. The underlying Swedish study of 97 patients across four university hospitals found that at 30 days, 39 (40%) were in complete clinical and endoscopic remission, 33 (34%) had had a colectomy and 25 (26%) had not reached remission, which sums correctly to 97, and that sustained fever, persistent bloody diarrhoea and continued CRP elevation on day three strongly predicted steroid resistance (Lindgren 1998).
• Edinburgh, or Ho, score. Built from mean stool frequency, colonic dilatation within the first three days and low albumin, in 167 consecutive patients of whom 67 (40%) failed medical therapy. Scores of 0 to 1, 2 to 3 and 4 or more carried medical failure rates of 11%, 43% and 85% (Ho 2004).

All three share a shape worth noticing: they are calculated on day three, in hospital, and they exist to decide whether to escalate. None of them is a home triage tool, and none of them was designed to tell you whether to get in the car. That is why this article leans on pulse, temperature, count and the go-now list instead.

For the day-to-day version of measuring your own disease, including where urgency fits, which the two-item PRO-2 score omits entirely, see our guides to the PRO-2 score in ulcerative colitis and reducing urgency with ulcerative colitis.

When to see a doctor promptly

Contact your IBD team or a doctor promptly if you have:

• Six or more bloody stools a day, or a stool count that has risen sharply over a few days
• Blood at every stool, blood that is darker than usual, or clots
• A temperature above 37.8C alongside a flare, or repeated drenching night sweats, both of which have a differential worth going through with your team rather than attributing to the colitis by default, and which our guide to night sweats in IBD sets out in order, including abscess, infection on immunosuppression and drug fever
• A resting pulse over 90 that stays up
• Waking at night to open your bowels when you normally do not
• Unexplained weight loss, or being unable to eat enough to maintain your weight
• Symptoms that are not settling despite a steroid course
• Any new symptom outside the gut, including painful or red eyes, new joint swelling, or a painful skin lesion

Seek emergency assessment the same hour for a distended or severely tender abdomen, severe unremitting abdominal pain, faintness on standing, being unable to keep fluids down, large volumes of fresh blood, new breathlessness or chest pain, calf pain and swelling, or confusion.

If any of your symptoms started after the age of 50 and have not been investigated, or there is a family history of bowel cancer, mention that explicitly, because it changes which tests get ordered.

If the flare and the fear of the hospital are both getting on top of you, that is worth saying out loud to someone. In the US you can call or text 988. In the UK and Ireland, Samaritans is free on 116 123. findahelpline.com lists services by country, and local emergency services are always an option if you are in immediate danger.

The honest bottom line

The threshold is around six or more bloody stools in 24 hours plus at least one systemic sign, and the systemic signs are a temperature above 37.8C, a resting pulse over 90, a haemoglobin below 10.5 g/dL, and raised inflammatory markers meaning an ESR above 30 mm/h or a CRP above 30 mg/L. Two of those need a blood test, which is not a flaw in the criteria, it is the reason assessment exists.

Practically: count your bloody stools honestly including the night ones, take your temperature, and take your resting pulse sitting still. If the count is at or above six and any one of the measurable signs is present, you need assessment today. If any go-now sign is present, you need it now, regardless of the count. If your numbers are all normal and you feel awful, you have a real flare that needs your IBD team this week, and the numbers you wrote down are what will make that conversation short and productive.

And if you are still unsure after reading all of this, the community's answer and the clinical answer happen to agree. One reply in the very first thread we read put it best: it is a good time to go when you find yourself asking strangers on the internet whether you should.

This article is general information about a health condition, not medical advice for your situation. Only a clinician who can examine you and see your results can tell you whether you need to be in hospital. If you think you might, err toward being assessed.