Which bowel symptoms should you actually act on?

If you have been putting off doing something about a bowel symptom, this article is meant to help you work out whether it needs attention. It is not a substitute for seeing someone, but it should tell you how seriously to take what you are noticing.

The system changed in 2023

Bowel cancer referral used to work on symptoms alone. Certain combinations of symptom and age triggered an urgent referral; everything else did not.

NICE changed this in 2023. The approach is now FIT-led: most people with symptoms that could suggest colorectal cancer should be offered a FIT test, and referred on the urgent pathway if the result is 10 µg Hb/g or above.

The reason for the change is straightforward. FIT is better at identifying who is at highest risk than any individual symptom or any combination of symptoms. It sorts people more accurately than a symptom checklist can.

Symptoms that should prompt a test

Broadly, these are the things that warrant assessment and a FIT test:

• A change in bowel habit. Any change, in either direction. New diarrhoea counts. So does new constipation, which people often assume does not.
• Rectal bleeding, particularly blood mixed through the stool rather than only on the paper
• Unexplained weight loss
• Persistent abdominal pain, particularly alongside weight loss
• Iron deficiency anaemia, or anaemia found on a blood test without an obvious cause
• An abdominal mass

Age affects how these are weighted, and the precise combinations differ slightly between the four UK nations, which is one of several reasons this is a conversation to have with a doctor rather than a checklist to self-administer.

Symptoms where you should be examined, not tested

There is an important exception. If any of the following apply, guidance is that you should be assessed directly rather than triaged with a stool test first:

• A mass you can feel in the back passage
• An unexplained lump around the anus
• Ulceration around the anus

These need someone to look and examine. Doing a home test first only delays that. If this describes you, please book an appointment rather than ordering a kit.

Where the guidance leaves gaps

This is worth knowing, because it affects a lot of people.

The NICE criteria are specific, and there are situations that fall outside them where testing is still sensible. Guidance from the Association of Coloproctology and the British Society of Gastroenterology takes a broader view: consider FIT for any symptoms or signs that might suggest colorectal cancer, and refer if the result is 10 or above.

Two groups sit squarely in this gap:

Unexplained raised platelets. Thrombocytosis is associated with several cancers including colorectal, particularly in people over 40.

Unexplained rectal bleeding in the under-50s. Colorectal cancer is rising in younger adults. Around 70% of those cancers occur in the left colon, most commonly the rectum, and the most common presenting symptom is rectal bleeding, in around 38% of cases. NICE has called for more research into FIT in the under-40s, but does not say it should not be used.

The practical upshot: not meeting a specific criterion is not the same as not needing testing. If you have a symptom that worries you, it is worth discussing.

Should thresholds be different for younger people?

A reasonable question, and the current answer is no. There is not enough evidence to justify different FIT thresholds by age, sex or ethnicity. Guidance is that FIT can and should be used to risk-stratify adults of all ages with bowel symptoms.

That matters if you are under 50 and have been told you are too young to worry. Age is a factor in your overall risk. It is not a reason to skip the assessment.