What are the red flag symptoms with IBS?

Blood in your stool, weight loss you cannot explain, a new and lasting change in bowel habit, iron deficiency anaemia, a lump in your tummy or back passage, symptoms that wake you at night, and symptoms starting at 50 or over. None is part of IBS, so each should be checked by a doctor.

When is blood in your stool an emergency?

When the bleeding will not stop, there is a lot of it (the toilet water turns red or you pass large clots), your stool is black and tarry, or you feel faint. Then call emergency services or go to the emergency department. Smaller amounts still need a doctor.

Can IBS cause bleeding?

Bleeding is not a symptom of IBS. Even if you have IBS, blood in or on your stool should be checked by a doctor, because guidelines treat it as an alarm feature.

At what age is a change in bowel habit a concern?

Since NICE updated its suspected cancer guidance in 2023, a change in bowel habit at any adult age is a reason for a FIT stool test to guide referral. New IBS-like symptoms starting at 50 or over also deserve a closer look.

Is bloating a sign of ovarian cancer?

It can be. NICE asks GPs to test for ovarian cancer when someone has persistent bloating, early fullness, pelvic or tummy pain, or urinary urgency, particularly more than 12 times a month. New bloating of this kind is worth checking, especially from age 50.

Does waking up at night with diarrhoea mean it is not IBS?

Not necessarily, but it is atypical. The British Society of Gastroenterology lists nocturnal diarrhoea or pain as a reason for further tests to look for conditions such as microscopic colitis or bile acid diarrhoea.

If I have no red flags, does that mean I have IBS?

No. Having no alarm features is one part of the picture, but a diagnosis also needs a clinician, usually with a few blood tests and sometimes a stool test. See a doctor if your symptoms are new, lasting or worrying.

Is this checker stored or emailed?

No email is needed to see the result. It is shown straight away, and your answers are not saved to a medical record.

Gut Red Flags Checker: When to See a Doctor

Check bowel warning signs and know how soon to get help.

Free
About 2 minutes
No account
Updated October 3, 2026

The short answer

Heavy bleeding from the bottom, black tarry stool, vomiting blood, sudden severe tummy pain, or being unable to poo or pass wind need emergency care now. Blood in your stool, weight loss you cannot explain, a lasting change in bowel habit, anaemia, a lump, or symptoms that wake you at night need a doctor soon. These are not part of IBS and should be checked whatever your diagnosis.

How to use the Gut Red Flags Checker

1Tick anything happening now that may need emergency help.
2Tick any alarm features that apply, such as bleeding, weight loss, a change in bowel habit or symptoms at night.
3Add your age and a few details so the result can show the guidance that applies to you.
4Get one of three clear actions, with the exact features to mention to a doctor.

Get help now

These signs need emergency care. Call your local emergency number or go to the nearest emergency department, and do not drive yourself. This list follows the NHS guidance on when to call 999 or go to A&E.

Sign	Action
Bleeding that will not stop, or a lot of blood (red toilet water, large clots)	Emergency
Black, sticky, tarry, very smelly stool	Emergency
Vomiting blood or vomit like ground coffee	Emergency
Sudden or severe tummy pain, or it hurts to touch your tummy	Emergency
Cannot poo or pass wind at all	Emergency
Fainting, collapse, confusion, or cold, blotchy skin	Emergency
Cannot keep fluids down, dehydration not settling, bloody diarrhoea	Urgent advice today (NHS 111 in the UK)

See a doctor soon

These alarm features are what guidelines ask doctors to look for before calling symptoms IBS. Most people who have them do not have cancer, but they need checking rather than waiting. NICE's suspected cancer guidance was updated in 2023 so that a change in bowel habit or iron deficiency anaemia at any adult age leads to a FIT stool test to guide referral.

Alarm feature	What NICE or the BSG says
Rectal bleeding	From 50, unexplained rectal bleeding alone; under 50, with tummy pain or weight loss, leads to a FIT test
Weight loss you cannot explain	From 40, with tummy pain, leads to a FIT test; from 60, more than 5% in 6 months needs urgent investigation
Change in bowel habit	Any adult age leads to a FIT test
Iron deficiency anaemia	Any adult age leads to a FIT test; any anaemia from 60
Lump in the tummy or back passage	Assessment at any age
Diarrhoea or pain at night	Atypical for IBS, a reason for further tests (BSG)
Strong family history of cancer	A reason for GP referral to a specialist (BSG)
Symptoms starting at 50 or over	One of the features that best separated other disease from IBS in one study

Bloating and ovarian cancer

Ovarian cancer can look like IBS. NICE asks GPs to arrange tests when someone with ovaries has persistent bloating, feeling full quickly or loss of appetite, pelvic or tummy pain, or needing to pee more urgently or often, particularly more than 12 times a month and especially from age 50.

NICE also asks for ovarian cancer tests when IBS-like symptoms start for the first time at 50 or over, because IBS rarely begins at that age. The British Society of Gastroenterology guideline makes the same point about persistent bloating in women.

What this checker cannot do

It cannot rule anything in or out, and having none of these features does not mean your symptoms are IBS. If your symptoms are new, lasting or worrying, see a doctor. If you already live with Crohn's disease or ulcerative colitis, use your IBD team's flare plan as well.

Frequently asked questions

What are the red flag symptoms with IBS?: Blood in your stool, weight loss you cannot explain, a new and lasting change in bowel habit, iron deficiency anaemia, a lump in your tummy or back passage, symptoms that wake you at night, and symptoms starting at 50 or over. None is part of IBS, so each should be checked by a doctor.
When is blood in your stool an emergency?: When the bleeding will not stop, there is a lot of it (the toilet water turns red or you pass large clots), your stool is black and tarry, or you feel faint. Then call emergency services or go to the emergency department. Smaller amounts still need a doctor.
Can IBS cause bleeding?: Bleeding is not a symptom of IBS. Even if you have IBS, blood in or on your stool should be checked by a doctor, because guidelines treat it as an alarm feature.
At what age is a change in bowel habit a concern?: Since NICE updated its suspected cancer guidance in 2023, a change in bowel habit at any adult age is a reason for a FIT stool test to guide referral. New IBS-like symptoms starting at 50 or over also deserve a closer look.
Is bloating a sign of ovarian cancer?: It can be. NICE asks GPs to test for ovarian cancer when someone has persistent bloating, early fullness, pelvic or tummy pain, or urinary urgency, particularly more than 12 times a month. New bloating of this kind is worth checking, especially from age 50.
Does waking up at night with diarrhoea mean it is not IBS?: Not necessarily, but it is atypical. The British Society of Gastroenterology lists nocturnal diarrhoea or pain as a reason for further tests to look for conditions such as microscopic colitis or bile acid diarrhoea.
If I have no red flags, does that mean I have IBS?: No. Having no alarm features is one part of the picture, but a diagnosis also needs a clinician, usually with a few blood tests and sometimes a stool test. See a doctor if your symptoms are new, lasting or worrying.
Is this checker stored or emailed?: No email is needed to see the result. It is shown straight away, and your answers are not saved to a medical record.

Should I See a Gastroenterologist for IBS?
Most IBS is managed well in primary care. Here is what a GP can order and prescribe, the guideline-backed reasons to refer, and what a specialist actually adds.
How Much Blood in Stool Is Normal With UC?
In ulcerative colitis the target is no visible blood at all. Why the eye misjudges amount, what each bleeding pattern suggests, and when to call your team.
When to Go to the Hospital for a UC Flare
Six or more bloody stools a day plus a fever, a fast pulse or feeling systemically unwell is the threshold that makes a UC flare a hospital problem.
IBS Waking Me Up at Night: What It Means
Night-time IBS symptoms are treated as a red flag everywhere online. The studies that tested alarm features found they barely discriminate. What the evidence says.
How to Describe Stomach Pain to a Doctor
Describe stomach pain by where it sits, what it feels like, its pattern, what changes it and what it stops you doing. The words and numbers that carry.

Sources

National Institute for Health and Care Excellence. Suspected cancer: recognition and referral. NICE guideline NG12. London: NICE; 2015, updated 2026. https://www.nice.org.uk/guidance/ng12
National Institute for Health and Care Excellence. Irritable bowel syndrome in adults: diagnosis and management. Clinical guideline CG61. London: NICE; 2008, updated 2017. https://www.nice.org.uk/guidance/cg61
Vasant DH, Paine PA, Black CJ, Houghton LA, Everitt HA, Corsetti M, et al. British Society of Gastroenterology guidelines on the management of irritable bowel syndrome. Gut. 2021;70(7):1214-40. doi:10.1136/gutjnl-2021-324598
Hammer J, Eslick GD, Howell SC, Altiparmak E, Talley NJ. Diagnostic yield of alarm features in irritable bowel syndrome and functional dyspepsia. Gut. 2004;53(5):666-72. doi:10.1136/gut.2003.021857
Ford AC, Veldhuyzen van Zanten SJ, Rodgers CC, Talley NJ, Vakil NB, Moayyedi P. Diagnostic utility of alarm features for colorectal cancer: systematic review and meta-analysis. Gut. 2008;57(11):1545-53. doi:10.1136/gut.2008.159723
NHS. Stomach ache. https://www.nhs.uk/conditions/stomach-ache/
NHS. Bleeding from the bottom (rectal bleeding). https://www.nhs.uk/symptoms/bleeding-from-the-bottom-rectal-bleeding/
NHS. Vomiting blood. https://www.nhs.uk/conditions/vomiting-blood/
NHS. Diarrhoea and vomiting. https://www.nhs.uk/conditions/diarrhoea-and-vomiting/
NHS. Dehydration. https://www.nhs.uk/conditions/dehydration/

Cite this tool

Clairop. Gut Red Flags Checker. www.clairop.com/tools/gut-red-flags-checker. Updated October 3, 2026.

Clairop is a general wellness app for people living with a diagnosed digestive condition. It does not replace professional medical care, diagnosis, or treatment. Always follow your healthcare provider's advice.

Clairop logs meals, symptoms and stool in seconds, then looks for the foods your gut reacts to, including reactions that land days later.

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