IBS Waking Me Up at Night: What It Means

If your IBS is waking you at night, almost every page you have read will have told you the same thing: night-time symptoms are a red flag, and real IBS does not wake you up. That claim is repeated so confidently that people arrive at appointments braced for bad news, or quietly convinced their diagnosis is wrong.

It is worth taking seriously. It is also considerably weaker than it sounds.

Two things are true at once. Waking from sleep with cramps or urgency is a symptom worth describing to a doctor, because a handful of conditions that look exactly like IBS are more likely to behave this way. And it does not rule out IBS, because the alarm-feature rule was tested, and it performed badly as a filter. Meanwhile the physiology that supposedly makes night symptoms impossible turns out, when somebody actually measured it, to say something more interesting than "your gut switches off at night".

Why "night symptoms mean it is not IBS" is only half true

The rule exists because it is a useful prompt, not because it is accurate. When the red-flag approach has been formally tested, it has consistently turned out to flag far more people than it finds.

The clearest test came from a chart review of 1,434 patients who had clinical diagnoses of IBS, abdominal pain, diarrhoea or constipation, and who also completed questionnaires identifying Rome II criteria and red flag symptoms. Red flags were reported by 84% of the sample. The positive predictive value of individual red flags for identifying organic disease was 7% to 9%. Among those with IBS, gastrointestinal cancer was found in 1.0%, inflammatory bowel disease in 1.2% and malabsorption in 0.7%. The authors concluded that red flags may be useful for deciding who needs extra evaluation, but that building them into the diagnostic criteria would leave 84% of people who their own physicians had diagnosed with IBS without any diagnosis at all (Whitehead 2006).

A second study looked specifically at what happens next. Two hundred consecutive patients who met Rome III criteria for IBS were reviewed for red flags: rectal bleeding, iron-deficiency anaemia, weight loss, family history of colon cancer, fever, and onset after age 50. Of those, 139 (70%) had at least one. Importantly for this article, the researchers also reviewed people with nocturnal symptoms and faecal soiling, describing them in the paper as features that are not traditional warning signs. When testing was performed, the yield was low, with few clinically significant findings (Black 2012).

That is worth sitting with. A peer-reviewed gastroenterology paper reviewing alarm features in IBS explicitly treats nocturnal symptoms as outside the traditional warning-sign list, while dozens of consumer health pages present them as the canonical example of one.

The pattern repeats elsewhere. In a Saudi general medicine clinic, 255 adults already diagnosed with IBS were screened with a validated red flag score designed to pick out people more likely to have Crohn's disease than IBS. On that instrument, 54.9% scored above the threshold that would make them candidates for further investigation (Mosli 2017). These were people from a general medicine clinic in one country, so the exact proportion will not transfer, but the direction is the same everywhere it has been measured: alarm features are common in people who have IBS.

The practical translation: raise it with your doctor, and expect them to think about it rather than panic. Both major guideline approaches build in a safety net without making night symptoms the deciding factor. The ACG guideline recommends a positive diagnostic strategy rather than diagnosis by exclusion, and suggests coeliac serology and faecal calprotectin in people with IBS and diarrhoea (Lacy 2021). NICE recommends a full blood count, inflammatory markers and coeliac antibodies in people who meet the criteria, and states that colonoscopy is not necessary to confirm the diagnosis in that group (NICE CG61). The Rome IV criteria themselves define IBS by recurrent abdominal pain related to defecation or to a change in stool frequency or form, with no clause about the time of day (Mearin 2016).

Your colon is not switched off all night

The mechanism behind the red-flag rule is usually stated like this: colonic motility is suppressed during sleep, so a bowel movement that wakes you has to be driven by something abnormal. The first half of that sentence is correct. The second half does not follow from it, and the study most often used to support it actually says something more specific.

Eleven healthy volunteers had pressure recorded from the entire colon while their sleep was staged in a laboratory. Propagating contraction frequency and overall pressure activity were significantly reduced at night, and the depth of sleep correlated strongly with how much they were suppressed. Propagating contractions were eliminated entirely during slow-wave sleep. But during REM sleep, colonic pressure and propagating contraction frequency rose sharply, back to levels comparable with stage 2 sleep. And transient arousal from stable sleep, with or without actually waking, was described by the authors as a potent and immediate stimulus for colonic propagating contractions (Furukawa 1994).

So the colon has a floor, not an off switch. It goes quietest in deep sleep, which is concentrated in the first part of the night, and it becomes measurably more active in REM sleep, which is concentrated in the second part. It also responds immediately to arousal.

That is a coherent explanation for the single most repeated detail in patient accounts. In a widely read r/ibs thread asking whether IBS had ever woken people in the middle of the night, the most upvoted replies clustered on a specific window, with 3am and 4am named repeatedly (r/ibs thread). Elsewhere on the same subreddit, one post title simply calls 3am "the shitting hour" (r/ibs thread). That is folklore, not data. But it lines up with where REM sleep sits in the night, and with the finding that arousal itself provokes the contractions.

We cover the morning version of this pattern, where waking up is itself the trigger, in why IBS flares up in the morning. The night-time case is the same physiology read at a different hour: instead of one large arousal at 7am, you get smaller ones scattered through REM-rich sleep.

Which came first: the pain or the waking?

This is the question that changes the interpretation, and almost nothing online asks it.

Two quite different events get filed under "IBS woke me up". In the first, gut pain or urgency builds until it breaks through sleep. In the second, you wake for an unrelated reason, and once you are awake and lying still in the dark, your gut starts hurting. People describe the second version often. In that r/ibs thread, one of the most upvoted comments said exactly that: waking because of insomnia, then the stomach pain starting a few minutes later (r/ibs thread).

The distinction matters because the small-bowel evidence points towards the second. Eight people with IBS and ten healthy volunteers had motility recorded from six sensors in the small intestine overnight while their sleep was staged simultaneously. Nocturnal small intestinal motility was similar between the groups. The motility index during wakefulness was higher than during every sleep stage. Sleep architecture in the IBS group was normal. The authors noted that in IBS, episodes of intestinal dysmotility had been described almost exclusively during wakefulness (Gorard 1995).

A study in six healthy subjects reached a compatible conclusion about the fasting motility cycle. Sleep shortened the cycle length and the duration of its second phase, but the cycles were distributed across sleep stages in a pattern consistent with randomness, meaning the gut rhythm and the sleep rhythm run independently rather than one driving the other (Kumar 1990).

Put together with the colonic findings, a reasonable reading is: the colon becomes more active in REM and after arousals, the small bowel keeps a rhythm of its own, and the dramatic dysmotility people associate with an attack is mostly a waking-state phenomenon. Which would mean that for many people, the sequence is arousal first, then the gut catching up.

The sleep studies in IBS disagree with each other, and that is the finding

If you go looking for what sleep laboratories have found in people with IBS, expect a mess. Five reasonably well-known studies produced four different answers.

Notice the sizes: six to twenty people each. Notice also that the Rotem comparison group was not healthy sleepers but adults with mild benign snoring, which makes that contrast harder to interpret than it first appears (Rotem 2003).

So: is REM increased, is REM latency longer, is slow-wave sleep destroyed, or is everything normal? The literature says all four. Nobody should tell you confidently what happens to your sleep architecture when you have IBS, because these studies do not agree.

What does survive is the gap between report and recording. Elsenbruch found significantly worse subjective sleep quality on the Pittsburgh Sleep Quality Index with no significant differences on any polysomnographic parameter, and interpreted this as altered sleep perception consistent with IBS involving exaggerated responses to normal internal stimuli (Elsenbruch 1999). Heitkemper found self-reported and recorded indicators correlated less well in the IBS group than in controls (Heitkemper 1998). A larger actigraphy study found something similar in a different direction: people with IBS actually slept more hours per day than healthy controls (7.7 versus 7.1) yet felt less well rested, while recording more waking episodes during sleep (12.1 versus 9.3) (Patel 2016).

This is not a way of saying the nights are imagined. It is a specific, repeatedly observed feature of the condition: the same internal events register more strongly. If your gut is more sensitive to distension while you are awake, it is unsurprising that a run of REM-driven colonic contractions at 4am registers as an event rather than as nothing.

The arrow runs from sleep to gut more clearly than the other way

Most people assume their gut is ruining their sleep. The diary evidence, such as it is, points slightly the other way.

Twenty-four community-recruited women aged 18 to 45 with IBS kept sleep and symptom diaries for one menstrual cycle and wore actigraphs for seven days. Poorer self-reported sleep quality significantly predicted worse next-day symptoms, and this held using the objective actigraphy measure as well. Symptoms did not predict sleep in the opposite direction. The authors called it a small exploratory study and asked for longitudinal research, which is the right level of confidence to hold (Buchanan 2014).

The larger actigraphy study reached a compatible conclusion. Across 24 people with IBS and 26 healthy controls monitored for a week with daily bowel pain logs, waking episodes during sleep correlated negatively with both general and IBS-specific quality of life, and disturbed sleep was associated with worse mood and greater non-gut pain as well as bowel symptoms (Patel 2016).

Both are small. Neither randomised anything, so neither can prove direction. But they are the best available answer to a question people ask constantly, and the answer is not the intuitive one. This also means a bad night has costs beyond the night itself, which is worth knowing when you are deciding whether to drag yourself through the next day on four hours of sleep.

Can a meal eaten at dinner cause a 3am attack?

Possibly, and the timing is not implausible. But timing on its own cannot identify a culprit, which is the mistake most night-time trigger hunting makes.

The person who started the most-read r/ibs thread on this described it precisely: when it happened, it was usually four to six hours after eating a trigger food, and it did not happen often (r/ibs thread). That interval is broadly consistent with food having left the stomach and small intestine and reaching the colon, where fermentable carbohydrates get worked on by bacteria and osmotically active sugars pull water in.

The problem is that this is one of several possible delays, not the only one. A symptom can arrive within minutes of the first mouthful, or hours later, or the following morning, depending on which mechanism is involved. We set out the whole timing picture in how long after eating IBS flares up, and the related question of why a meal can send you straight to the bathroom in why you have to poop right after eating. The short version for night symptoms: a 4am episode after an 8pm dinner is compatible with a food reaction, and also compatible with REM-associated colonic activity that would have happened anyway, and also compatible with both at once.

There is a second complication specific to evening meals. Eating late does not only change what is in your colon at 3am, it also changes your sleep. If the meal fragments your sleep, and fragmented sleep both raises next-day symptom scores and produces the arousals that stimulate colonic contractions, then the meal has at least two routes to the same 3am outcome and a single night's log cannot tell them apart.

None of this has been tested as an intervention. There is no trial of "stop eating three hours before bed" in IBS. Moving dinner earlier for a fortnight and logging the nights is a sensible, low-risk personal experiment, and it is worth being honest that it is an experiment rather than advice with evidence behind it.

Why night attacks come with sweats, chills and feeling faint

Severe cramping, then sweating, shivering, nausea and light-headedness is one of the most frightening versions of this, and it comes up repeatedly. In an r/ibs thread about severe night cramping leading to diarrhoea, vomiting, sweats and chills, commenters described cold sweats, feeling weak afterwards, near-fainting on the toilet, and in some cases actually fainting (r/ibs thread).

The mechanism usually invoked is a vasovagal response: intense visceral pain and straining prompt a reflex drop in heart rate and blood pressure, producing pallor, sweating, nausea and dimming vision. Syncope specifically related to defecation is a recognised situational form. In a comparison of 20 consecutive patients with defecation syncope and 37 with micturition syncope, the defecation group were significantly older (mean 63 years), 60% were women, episodes were distributed roughly evenly across the 24 hours rather than clustering at night, and gastrointestinal symptoms preceded the episode in 55% of cases compared with 3% in the micturition group (Komatsu 2010).

Two honest caveats. That was twenty people, referred because they had fainted, with a mean age well above the typical IBS population, so the percentages do not transfer to a thirty-year-old with IBS-D. And the finding that episodes did not cluster at night cuts against the idea that this explains the 3am timing specifically. What it does establish is that a vasovagal reaction around defecation is a real, described phenomenon with a gut prodrome, rather than something people are imagining.

The conditions that night symptoms genuinely make more likely

This is the legitimate core of the red-flag advice, and it deserves a fair hearing rather than either dismissal or alarm. Several conditions produce IBS-like symptoms and are described as more likely to disturb sleep. Being checked for them is reasonable. Assuming you have one is not.

Some of these numbers deserve a second look, because they are routinely misreported.

Bile acid malabsorption is the big one. Across six studies of 908 people meeting accepted criteria for IBS-D, the pooled rate was 28.1% (Slattery 2015). An earlier and larger systematic review of 18 studies and 1,223 patients found that in five of those studies, covering 429 patients, 10% had severe bile acid malabsorption, and concluded that idiopathic adult-onset bile acid malabsorption is not rare and that international IBS guidelines needed revising to reflect it (Wedlake 2009). A more recent meta-analysis of ten studies covering 1,034 people with IBS-D put the pooled rate at 32% by the same retention test, while noting that the blood-based alternatives use different cutoffs between studies and need further evaluation (Liu 2023). Roughly a quarter to a third is a large fraction of a common diagnosis.

Microscopic colitis is the one most often overstated. It is regularly described as commonly misdiagnosed as IBS. A meta-analysis of ten eligible studies found that one third of people with microscopic colitis reported symptoms compatible with IBS, but that the prevalence of microscopic colitis in people with IBS was not higher than in other patients presenting with diarrhoea. Pooling three cross-sectional surveys, the odds ratio for microscopic colitis in people with IBS compared with other patients with diarrhoea was 0.68, with a confidence interval crossing 1 (Kamp 2016). The overlap is real in the sense that the symptoms resemble each other. The claim that an IBS label specifically hides microscopic colitis is not supported by that analysis.

Calprotectin is very good at reassuring and poor at confirming. Across 17 studies and 1,956 patients, faecal calprotectin distinguished IBD from IBS with a summary sensitivity of 85.8% and specificity of 91.7%. At an IBD prevalence of 1%, the negative predictive value was 99.8% while the positive predictive value was only 9%. Sensitivity was higher in Western than Eastern countries and at cutoffs of 50 µg/g or below. All 17 studies were rated at high or unclear risk of bias (Dajti 2023). A commenter in one of the r/ibs threads made a version of this point from experience, saying calprotectin is better at prompting further investigation than at ruling anything out (r/ibs thread). That is broadly right in spirit, though the numbers say a normal result in a low-risk person is in fact quite reassuring, while an abnormal one mostly means more looking.

Coeliac disease should be excluded before IBS is confirmed. Across 29 studies and 7,209 people with Rome III or Rome IV IBS, pooled seroprevalence was 6% and biopsy-proven coeliac disease 2%, with odds of positive serology 4.42 times higher than controls. The authors noted a limited number of European studies and none from the United States, and that 15% of seropositive patients never went on to biopsy (Shiha 2025). The traffic runs both ways: in a meta-analysis of seven studies and 3,383 participants, 38% of people with established coeliac disease reported IBS-type symptoms (Sainsbury 2013).

If night symptoms are part of a wider picture of bloating and altered bowels, bacterial overgrowth is another overlap worth understanding, and we have covered where that evidence actually stands in SIBO versus IBS symptoms.

The one night-time symptom that is genuinely different

There is a version of this that should not be lumped in with the rest, and it is the one people are most reluctant to describe.

Passing stool during sleep, without an urge that wakes you first, is a different event from being woken by cramps and getting to the bathroom in time. It appears in patient accounts: one r/ibs post is simply about waking at 2am to find it had already happened (r/ibs thread). It was also one of the two features the red-flag yield study singled out alongside nocturnal symptoms as non-traditional warning signs worth reviewing (Black 2012).

Whatever the eventual explanation, it is worth telling a doctor promptly and describing it in those exact words rather than as "night-time symptoms", because the two get treated differently. NICE notes that about 20% of people experiencing faecal incontinence disclose it only if they are asked directly (NICE CG61), which is another way of saying that many clinicians will not find out unless you say it first.

Why it seems worse on work nights

Two plausible mechanisms overlap here, and the evidence separates them in a slightly surprising way.

Among 1,335 experienced Norwegian nurses surveyed in a long-running shift work cohort, 6.3% met Rome IV criteria for IBS. IBS was more prevalent in nurses with insomnia (9.7% versus 4.8%), with excessive sleepiness (10.7% versus 4.9%) and with shift work disorder (9.1% versus 5.0%). It was not significantly more common in those simply working a schedule that included night shifts (7.2% versus 5.9%) (Waage 2026). This was cross-sectional, so it cannot establish what caused what, and nurses are not a general population. But it points at disrupted sleep rather than the rota itself.

A much larger prospective analysis complicates that. Following 266,605 UK Biobank participants for a median of 9.03 years, 5,218 developed IBS. Compared with people who never or rarely worked night shifts, those who always did had a hazard ratio of 1.36 in the fully adjusted model. The association persisted across genders, age groups, sleep durations and mental health status, but was only observed in people with a body mass index of 25 or above (Lu 2025).

Two studies, two designs, two answers about the schedule itself. The consistent thread is that disturbed sleep travels with IBS. Neither study looked at night-time symptoms specifically, so this is background rather than a direct answer to why Tuesday is worse than Saturday.

The other candidate is anticipation, which is harder to measure. Several people in the r/ibs threads described a self-perpetuating loop: a night attack, then anxiety the following day about it recurring, then a worse night. One described waking with a pounding heart and panicking before the gut symptoms fully arrived (r/ibs thread). This is lived experience rather than evidence, but it fits the broader picture we cover in whether stress can cause an IBS flare, and it fits the finding that arousals themselves stimulate colonic contractions (Furukawa 1994). Lying awake dreading 3am is, physiologically, not a neutral activity.

What the evidence says about helping the nights

This is where honesty costs the most, because the studies are small and the temptation to oversell is high. None of what follows is a recommendation to start anything. Decisions about medicines and supplements belong with your doctor, who knows your history.

Melatonin has the most interesting result, and it is not the one you would expect. Forty people with IBS and sleep disturbance were randomised to melatonin or matching placebo at bedtime for two weeks, with rectal manometry and overnight polysomnography before and after. Melatonin significantly reduced the mean abdominal pain score and reduced rectal pain sensitivity. It did not improve sleep disturbance, and it did not improve psychological distress. The authors concluded that the benefit on abdominal pain was independent of any effect on sleep (Song 2005).

That is a mechanism check worth pausing on. The obvious story is that melatonin helps IBS by fixing sleep. The trial that measured both found the pain improved and the sleep did not. Whatever melatonin is doing in IBS, in that study it was not working through sleep.

A larger, more recent trial complicates it. One hundred and thirty-six people meeting Rome IV criteria were split by whether they had a sleep disorder, then randomised within each group to melatonin or placebo for eight weeks. IBS scores and most gut symptoms improved in both groups, including abdominal pain severity and frequency, bloating severity and stool consistency, though not weekly defecation frequency. Sleep parameters improved only in the participants who had a sleep disorder to begin with (Faghih Dinevari 2023). So a sleep benefit does appear, but only where there was a deficit to correct, and the gut benefit again did not depend on it.

Treating the insomnia directly has one small trial. Sixty college students with IBS and comorbid insomnia were randomised to four weekly sessions of cognitive behavioural therapy for insomnia or to no such therapy. The treated group showed significant improvements in insomnia severity, sleep onset latency, pre-sleep arousal, gastrointestinal symptoms during sleep, IBS symptom severity and IBS quality of life. Interleukin-6 and C-reactive protein did not differ between the groups (Yang 2022). Read that with its limits in view: sixty students in one country, an unblinded design with a no-treatment comparison, and self-reported primary outcomes, which is the setup most likely to flatter an intervention. It is a promising signal about the direction to look, not proof.

Guideline-level treatments are not night-specific. The ACG guideline recommends a limited trial of a low FODMAP diet for global symptoms and suggests gut-directed psychotherapy (Lacy 2021). A low FODMAP diet is a short, structured process with a planned reintroduction phase, ideally supervised by a dietitian, and it is not a permanent way of eating. NICE advises titrating antimotility or laxative treatment to stool consistency, aiming for Bristol type 4 (NICE CG61). None of these were tested against night-time symptoms as an endpoint, so any effect on your 3am episodes is an inference.

A worked example: three weeks of night logs

Here is what separating these threads actually looks like. The pattern below is illustrative, built to show the method rather than describing a real person.

Someone with IBS-D is woken roughly twice a week, usually between 3am and 4.30am, by cramping that resolves after a bowel movement. They are convinced it is dairy, because the two worst nights followed ice cream.

Week one, recording only. They log, for each night: bedtime, time of last food, what it was, wake time if woken, whether pain came before or after waking, Bristol type, and how long until they got back to sleep. They add nothing else and change nothing.

Result: four episodes. Two followed a late dinner after 9pm. One followed a normal 7pm dinner. One came on a night they had barely eaten. In three of the four, they had woken first and the pain started afterwards. Ice cream featured in one.

Week two, one variable. They move dinner to before 7.30pm every night, change nothing else, and keep logging.

Result: three episodes, still clustered between 3am and 5am. Slightly milder by their own rating. Dairy appeared twice during the week without a night episode following.

Week three, back to normal. They return to their usual dinner timing to see whether episodes increase again.

Result: three episodes. No clear difference from week two.

What the three weeks bought them. Not a trigger. Something better: ten episodes logged, in seven of which waking preceded the pain, a stable time window unaffected by dinner timing, and a clean demonstration that dairy was present on more nights without episodes than with. That is a much stronger thing to bring to an appointment than "I think it might be dairy". It shifts the conversation from an elimination diet towards the two questions actually worth asking: is anything else going on that should be excluded, and is the sleep itself treatable.

It is also a demonstration of why single-night associations mislead. The two ice cream nights were memorable precisely because they were bad. The dozen ordinary dairy nights left no impression at all. We set out this problem, and how to design around it, in how to keep a food diary for IBS.

What to write down, and why each field earns its place

The reason to write it down rather than remember it is that memory over-samples the dramatic nights and discards the ordinary ones, which is exactly the bias that produces a false trigger. If you would rather not run a paper log at 4am, Clairop is built for logging fast in the moment and for producing a summary you can take to an appointment; you can see how that works on our how it works page. Any method that captures the night while it is happening will beat a reconstruction on Sunday.

Myths about night-time IBS

"If it wakes you at night it is not IBS." The most widely repeated claim here, and the least supported. Red flags were present in 84% of one large sample with a positive predictive value of 7% to 9% for organic disease (Whitehead 2006), and the study that reviewed alarm-feature yield in Rome III IBS explicitly treated nocturnal symptoms as not a traditional warning sign (Black 2012). Raise it. Do not conclude from it.

"Your colon shuts down during sleep." It reduces activity and goes silent in slow-wave sleep, but propagating contractions return during REM to levels seen in light sleep, and arousal is an immediate stimulus for them (Furukawa 1994). The pages that build the red-flag rule on a total shutdown are citing half of the finding.

"Microscopic colitis is what is really going on." A meta-analysis found no higher prevalence of microscopic colitis in people with IBS than in other people with diarrhoea (Kamp 2016). It is a condition worth knowing about and one your doctor may consider. It is not the hidden answer behind most night symptoms.

"A normal calprotectin means nothing." It means quite a lot in someone at low prior risk: a negative predictive value of 99.8% at 1% IBD prevalence. What it cannot do is confirm anything, with a positive predictive value of 9% at that prevalence (Dajti 2023). Reassuring when normal, ambiguous when raised.

"Fix your sleep and the gut follows." Partly supported and often overstated. Sleep quality predicted next-day symptoms in a small diary study while symptoms did not predict sleep (Buchanan 2014), which is encouraging. But the melatonin trial that measured both found abdominal pain improved without sleep improving (Song 2005). The relationship is real and it is not a lever with a guaranteed result.

"Night-time symptoms mean the food you ate at dinner." Sometimes, plausibly. But a 4am episode is equally compatible with REM-associated colonic activity, with a fragmented night, or with a combination, and one night's coincidence is not evidence. Our guide on why safe foods sometimes trigger IBS explains why the same food produces different outcomes on different days.

"Everyone with IBS gets this." It is common enough to fill long threads, and it is not universal. Many people with IBS never have a night episode. Its presence or absence is not a measure of how severe your IBS is.

If you have Crohn's disease or ulcerative colitis

The calculation is different when inflammation is in the picture, and night-time symptoms carry more weight rather than less.

In 136 Japanese patients with IBD, 44.1% had sleep disturbance on the Pittsburgh Sleep Quality Index. Over the following year, 37.5% had a disease flare, and sleep disturbance was a significant risk factor for flaring with an odds ratio of 3.09 (Uemura 2016). That was a single-centre questionnaire study with self-reported flares, so it establishes an association rather than a cause. A review of the wider field notes that altering circadian rhythm significantly worsens colitis in animal models and that people with IBD appear to be at increased risk of altered sleep patterns, while stating plainly that more research is needed (Swanson 2011).

If you have IBD and you are being woken at night, particularly with bleeding, weight loss, fever or a change from your usual pattern, that is a reason to contact your IBD team rather than to adjust your diet and wait. We have separate guides on telling whether you are in a Crohn's flare and on recognising a ulcerative colitis flare, both of which cover how symptoms and inflammation can diverge in either direction.

When to see a doctor

Being woken by cramps is worth mentioning at your next appointment. Some things are worth more than a mention, and should be raised promptly rather than filed under a bad patch:

• Blood in your stool, or black tarry stools.
• Unexplained weight loss you did not intend.
• Passing stool while asleep, without an urge waking you first.
• Fever alongside the episodes.
• Fainting, or repeatedly coming close to fainting, during or after an episode.
• New anaemia, or symptoms of it such as breathlessness and unusual fatigue.
• Symptoms that started after the age of 50, or a family history of bowel cancer, ovarian cancer or IBD.
• A clear change from your usual pattern, particularly night episodes that were rare and are now frequent.
• Persistent vomiting, or pain severe enough to send you to an emergency department.

See a doctor promptly if any of these apply. None of them means the worst, and all of them mean the question deserves answering rather than absorbing.

When you go, bring the log. It changes the conversation from a description to a dataset. The two lines that do the most work are the time window your episodes fall in and whether pain preceded or followed waking, because both are specific, neither can be reconstructed from memory, and together they tell a clinician something they cannot get from an examination.

The short version

Night-time IBS symptoms sit in an awkward gap. They are treated online as a diagnostic verdict, and treated in the research literature as a feature that is common, non-specific and not on the traditional warning list. The reality is in between: worth checking, not worth panicking about.

The mechanism most pages teach, that the colon shuts down during sleep, is half of a real finding. Propagating contractions are eliminated in deep sleep and return during REM, and arousal triggers them immediately (Furukawa 1994). That gives the early hours, where REM is concentrated, a genuine physiological claim on your symptoms without requiring any other diagnosis.

The most useful thing you can do is not an elimination diet. It is to log ten episodes with one extra field in them: whether the pain came before you woke or after. That single distinction, a stable time window, and an honest count of how many trigger-food nights passed without incident will give you and your doctor more to work with than any list of night-time IBS foods on the internet.