A change in bowel habit is one of the few symptoms that guidance treats seriously at any age, in either direction, and with no age cut off attached to it. Most changes turn out to be something benign. The point of a test is to find out which sort you are dealing with.
A change in bowel habit is listed in NICE guidance as a reason to offer a FIT test, with no lower age limit attached. Most of the other criteria come with an age qualifier. This one does not.
It counts in both directions. People assume it means new diarrhoea. New constipation counts too, as does going more often, going less often, a change in what your stools look like, or a feeling that you have not fully emptied.
The reason guidance moved to a test rather than a symptom checklist is that individual symptoms are poor predictors of bowel cancer. A number sorts people more accurately than any description of what has changed. We report yours against 10 µg Hb/g, the symptomatic threshold, and give you the actual figure.
Guidance is clear that certain findings go straight to assessment without a stool test first. Please speak to a doctor rather than ordering a kit if any of these apply:
You can book a consultation with our GP, or contact your own surgery. If you feel acutely unwell, call NHS 111 or 999.
What guidance actually says, and what it deliberately leaves open.
NHS screening and symptomatic testing use identical kits and identical analysers. Only the threshold changes. Screening in England is moving from 120 to 80 µg Hb/g by March 2028. When you have a symptom, NICE sets the line at 10.
New constipation qualifies just as much as new diarrhoea. So does going more often, going less often, a change in stool consistency, or the sense that you have not finished. People routinely discount the constipation half of that.
Most FIT criteria in NICE guidance carry an age qualifier. A change in bowel habit does not. Adults of any age with a persistent change qualify, and the threshold is the same number whatever your age.
This is the reason national guidance moved from a symptom led pathway to a test led one. No description of what has changed sorts people as accurately as a measurement does.
If the change persists, it still needs explaining. Guidance expects safety netting and reassessment rather than a single test and a shrug.
The phrase is doing a lot of work and it is worth unpacking, because people rule themselves out of it for the wrong reasons.
A change in bowel habit means a persistent difference from what is normal for you. There is no correct number of times a week to open your bowels. The range across healthy adults runs from three times a day to three times a week, and the question is not where you sit in that range but whether you have moved within it and stayed moved.
The common threshold used in practice is around three to four weeks of persistence. Something that lasted five days and settled is a different situation from something that has been going on since the spring.
Most persistent changes in bowel habit are not bowel cancer, and it would be dishonest to build a page that implied otherwise. The usual causes are irritable bowel syndrome, dietary change, medication, coeliac disease, bile acid malabsorption, thyroid problems, inflammatory bowel disease and, in older adults, simple changes in mobility and fluid intake.
Several of those are worth diagnosing in their own right. Coeliac disease is easily missed and easily treated. Bile acid malabsorption is frequently mislabelled as irritable bowel syndrome for years. A stool test does not find any of them, which is a genuine limitation of testing alone and one of the reasons a consultation is included with the result rather than sold separately.
The argument for measuring rather than describing is straightforward. A meta-analysis of 28,832 symptomatic patients found that at the 10 µg Hb/g threshold, FIT detected 88.7% of colorectal cancers. Read the same samples at 150 and that falls to 66.3%. The test is the same. Only the line moved.
The corresponding reassurance at the low end is meaningful. Data from symptomatic patients in NHS Greater Glasgow and Clyde put the prevalence of colorectal cancer at around 0.2% in those with a result under 10, and around 1% between 10 and 19. Low is not zero, and we will not pretend it is, but it is a very different starting point from not knowing.
Two things. We report against 10 rather than a screening threshold, and we give you the actual figure rather than a category. Those detection rates vary enormously across the range of results that all get labelled positive, so knowing whether you are at 12 or at 400 is genuinely useful information rather than a technical detail.
And a GP telephone consultation is included whatever your number is. If your bowels have changed, the number is only half of what you need. The other half is somebody asking what changed, when, what you are taking, what else is going on, and whether coeliac screening or blood tests should be part of the picture.
Come back to it. A normal result lowers the odds of cancer, it does not explain what is happening to you, and it does not mean you should stop asking. Guidance expects safety netting and reassessment rather than a single test and a closed file. Persistent symptoms with a normal result warrant a doctor, not just another sample.
Sourced at the foot of the page. Where a figure comes from one regional service rather than the whole UK, it says so.
This test answers one question well. It does not answer the question of what is actually wrong.
The figure used in practice is usually around three to four weeks of persistence. Scottish qFIT guidance uses four weeks for a persistent change. Something that lasted a few days and settled is different from something that has continued. If you are unsure, that itself is a reasonable reason to get it checked rather than to keep waiting.
Both count. This is one of the most common misunderstandings about the criterion. NICE lists a change in bowel habit without specifying a direction, and new constipation qualifies just as much as new diarrhoea. Alternating between the two counts as well.
You are not too young to be assessed. NICE attaches no age limit to change in bowel habit as a reason to offer FIT, and the threshold used to interpret the result does not vary by age either. Bowel cancer is genuinely uncommon under 50, accounting for around 1 in 20 UK cases, and rates in younger adults have been rising. Being young is context for interpreting a result, not a reason to skip getting one.
It very often is, and irritable bowel syndrome is a real diagnosis rather than a shrug. But it is a diagnosis that should be made after considering the alternatives, not instead of considering them. Coeliac disease and bile acid malabsorption are both commonly mislabelled as IBS for years. A stool test does not diagnose any of these, which is why a consultation is included with your result.
Then the question is still open and you should go back to a doctor. A normal result makes cancer less likely, it does not explain your symptoms, and national guidance expects safety netting and reassessment rather than a single test closing the matter. Around 1 in 10 people with colorectal cancer have a result below the threshold.
It is the same test, analysed by The Doctors Laboratory, a UKAS accredited medical laboratory (No. 9317, ISO 15189:2022), on the same type of analyser. The difference is the number it is read against and what you are given. NHS screening currently uses a much higher threshold, being lowered from 120 to 80 µg Hb/g in England by March 2028, and returns a normal or abnormal letter. We report at 10 and give you the actual figure, a written GP report, and a consultation.
Figures are drawn from the sources above. Framing and commentary are the author’s own. Written and reviewed by Dr Rhea Bhadresha, GP. Last reviewed August 2026.
One small sample, collected at home. Your exact figure read against the symptomatic threshold, with a written GP report and a telephone consultation included.
Your exact FIT figure, a written GP report and a telephone consultation are all included, whatever the number turns out to be. A one-off test with no subscription and nothing recurring.