Most rectal bleeding is not cancer. But assuming it is haemorrhoids is described in surgical guidance as the single most commonly missed route to a bowel cancer diagnosis, and the old advice that a stool test is pointless once you can see blood has been overturned.
Seeing blood does not make a stool test redundant. That used to be the advice and it is no longer what guidance says. Since 2022, national guidance has recommended offering FIT to people who present with rectal bleeding, because FIT measures a haemoglobin breakdown product from higher in the bowel rather than fresh blood on the surface of the stool.
In the NICE FIT study, 26.9% of patients with rectal bleeding had a positive FIT, against 15.2% of those without it. The test still separates people usefully. It is not drowned out by the bleeding you can see.
The thing worth knowing: NHS screening reads the same test against a much higher number than a doctor does when you have a symptom. We report at 10 µg Hb/g, the threshold NICE sets for people with symptoms, and give you the actual figure rather than a pass or a fail.
National guidance is explicit that certain findings should go straight to assessment without waiting for a stool test. Do not order a kit if any of these apply. Contact your GP, or book a consultation with us today:
If you feel unwell with the bleeding, or it is heavy, call NHS 111 or 999 rather than waiting for anything. A test result is never a reason to delay being seen.
Plainly, and with the sources listed at the bottom of the page.
The NHS screening kit and the kit a GP hands you are the same test on the same analysers. What changes is the number at which a result is called positive. Screening in England is moving from 120 to 80 µg Hb/g, a rollout due to complete by March 2028. When you have a symptom, NICE sets the threshold at 10.
The 2022 ACPGBI and BSG joint guideline recommends FIT for people presenting with rectal bleeding. FIT detects a breakdown product of haemoglobin from further up the bowel, so surface bleeding from the anus does not simply swamp the reading.
Surgical guidance puts it bluntly: bleeding attributed to haemorrhoids is the most often missed opportunity to make a bowel cancer diagnosis. Having piles does not stop you also having something else.
A meta-analysis of 28,832 symptomatic patients found sensitivity of 88.7% at 10 µg Hb/g. At 100 and 150 it fell to 68.1% and 66.3%. The threshold you are measured against changes the answer.
If you are bleeding and the test is low, something is still causing the bleeding. That is a reason to have it looked at properly, not a reason to forget about it.
For years the reasoning went like this: a stool test looks for blood you cannot see, so if you can already see blood, the test tells you nothing you did not know. It sounded sensible. It turned out to be wrong.
FIT does not detect blood in the way that word suggests. It detects human haemoglobin, and specifically a globin breakdown product that survives the journey through the bowel. Fresh bleeding from the anus or from a haemorrhoid tends to coat the outside of the stool, and the sampling probe takes its sample from the middle. There is also a plausible chemistry argument: fresh bleeding produces intact red cells, while blood from higher up has broken down into exactly what the assay is built to find.
Whatever the mechanism, the observed behaviour is clear. In the NICE FIT study, which recruited 9,822 symptomatic patients across 50 sites in England, the test still discriminated in people who were bleeding. In 2022 the ACPGBI and BSG joint guideline changed the recommendation, and NHS England wrote to practices asking for it to be implemented in full.
The honest answer is that most rectal bleeding in adults is not cancer. Haemorrhoids and anal fissures account for a very large share of it. Inflammatory bowel disease, diverticular disease, polyps, infections and, less often, cancer make up the rest.
The problem is not the base rate. The problem is what happens when the base rate is used as a reason to stop looking. Guidance from the American Society of Colon and Rectal Surgeons states it about as directly as a guideline ever does: rectal bleeding attributed to haemorrhoids represents the most often missed opportunity to establish a cancer diagnosis. The mistake is not thinking of piles. The mistake is stopping there.
Two things make this worse. Haemorrhoids are extremely common, so almost anyone examined will have some. And having them explains nothing about whether something else is also present. A raised FIT in someone with visible piles still needs investigating.
People describe blood in enormous detail and hope the description settles the question. It narrows things a little, and less than you would like.
| What you noticed | What it tends to suggest | Does it settle it? |
|---|---|---|
| Bright red, on the paper or on the surface of the stool | More often anal or low rectal, such as haemorrhoids or a fissure | No. It shifts the odds, it does not close the question |
| Darker red, mixed through the stool | More often from further up the colon | No, but it is a reason to be more thorough |
| Black, tarry, sticky and strong smelling | Usually bleeding from the stomach or upper gut | This needs assessing urgently. FIT does not look there |
| Pain on opening your bowels alongside the blood | Often a fissure | No. Pain and cancer are not mutually exclusive |
Individual symptoms are poor predictors of colorectal cancer. That is the reason national guidance moved from a symptom led pathway to a test led one. A number is more use than a description.
You order a kit, collect one small sample at home, and post it back in the prepaid packaging. The laboratory reports the exact quantity of haemoglobin, and we give you that figure rather than a positive or negative. A written GP report comes with it, and a telephone consultation with a GP is included whatever the number is.
That last part is the point. A raised result arriving by email at nine at night, with no one to ask, is a bad way to find something out. If your number is raised we contact you and offer the earliest slot we have, rather than waiting for you to book.
Good. Keep going. This test is not a replacement for an NHS pathway that is already moving, and if you have been referred, take the referral. Where this is useful is when you have not been referred, when you want your actual number rather than a category, or when you want a doctor to talk it through with you properly.
Most raised results are not cancer. At a symptomatic threshold of 10 µg Hb/g the test is deliberately set to catch as much as possible, which means most people above it will turn out to have something else, or nothing found at all. The figure itself carries information: a result just above 10 sits in a very different risk band from one in the hundreds, and a GP can tell you which band you are in and what usually follows.
If your result is raised we write to your NHS GP with the figure and the laboratory report so they can act on it. If you have private medical insurance we can refer you for a private colonoscopy instead. Either way you are not left holding a number and a search engine.
Each one is sourced at the foot of this page. Where a figure comes from a specific study population rather than the general public, it says so.
We would rather you knew this before you paid than after.
Yes, and national guidance now recommends it. The 2022 joint guideline from ACPGBI and BSG recommends offering FIT to people presenting with rectal bleeding. FIT measures a haemoglobin breakdown product rather than fresh surface blood, so visible bleeding does not simply swamp the reading. In the NICE FIT study, 26.9% of patients with rectal bleeding had a positive result compared with 15.2% of those without.
It should not be assumed to. Haemorrhoids are an infrequent cause of a raised FIT, and surgical guidance describes rectal bleeding attributed to haemorrhoids as the most often missed opportunity to establish a bowel cancer diagnosis. Haemorrhoids are common enough that most people examined will have some, which means finding them tells you very little about whether anything else is present. A raised result in someone with piles still needs investigating.
Bright red blood on the paper is more often from the anus or low rectum, and darker blood mixed through the stool more often comes from further up. That shifts the probability, it does not settle the question. Individual symptoms are poor predictors of colorectal cancer, which is why national guidance moved to a test led approach rather than a symptom led one. Black, tarry stools are different again and usually point to the stomach or upper gut, which this test does not assess.
If you have developed symptoms since, yes. NICE is explicit that FIT should be offered even if someone has previously had a negative result through the NHS bowel cancer screening programme. The screening threshold is much higher than the symptomatic one, so a normal screening letter is not the same as being cleared once you have a symptom.
We report against 10 µg Hb/g, which is the threshold NICE sets for people with symptoms in England, Wales and Northern Ireland. Scotland uses 20. NHS screening uses a much higher number: it is being lowered from 120 to 80 in England in a rollout due to complete by March 2028, and Scotland and Wales are already at 80. The UK National Screening Committee has said the optimal screening threshold would be 20, and the constraint on getting there is colonoscopy capacity rather than anything about the test.
If you have any bleeding that is heavy or persistent, a lump you can feel, an unexplained sore around the anus, or you feel unwell, then yes, and you should do that first rather than testing. For everyone else a test is a reasonable step, and a consultation with a GP is included with your result either way. If your symptoms change or worsen while you are waiting, contact your GP or NHS 111 without waiting for the result.
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.
Reported at the symptomatic threshold, with a written GP report and a telephone consultation included whatever the figure turns out to be.
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.