When a family history changes what you should do.

Start with the detail, not the fact

"Bowel cancer runs in my family" covers a very wide range. What matters is who, how old they were, and how many. Before you do anything else, try to establish for each affected relative: their relationship to you, their age at diagnosis, and whether it was bowel cancer specifically rather than another abdominal cancer.

The patterns that usually change nothing

One relative diagnosed over the age of 50, particularly a grandparent, aunt or uncle, generally does not take you outside ordinary population screening. Bowel cancer is common; having one older relative who had it is common too. Mention it to your GP so it is on record, take part in NHS screening when invited, and act on symptoms.

The patterns that do

These warrant a conversation with your GP and often a referral to a clinical genetics or family history service:

• A parent, brother, sister or child diagnosed under 50.
• Two or more close relatives on the same side of the family with bowel cancer.
• A relative with multiple polyps, or bowel cancer alongside endometrial, ovarian, stomach or urinary tract cancers in the family — a pattern that can suggest Lynch syndrome.
• A known inherited condition in the family: Lynch syndrome, familial adenomatous polyposis or similar.

Lynch syndrome is the most common inherited cause, and carriers face a substantially elevated lifetime risk. It is also actionable: identified carriers are offered regular colonoscopy from a young age, which prevents cancers rather than merely finding them.

Why a stool test is not the answer for this group

Screening tests, ours included, are designed for people at ordinary population risk. If your background risk is materially higher, a normal stool test gives you a level of reassurance the test was never built to provide, and the right response is direct visualisation.

Colonoscopy does two things no stool test can. It sees the bowel wall, and it removes polyps during the same procedure. For someone with a strong family history, that is the point: you are not just looking for cancer, you are removing the things that would have become cancer.

This is why our suitability questionnaire routes people with a strong family history away from ordering and towards their GP. It costs us a sale and it is the correct advice.

What to say to your GP

Bring the details: who, what cancer, what age at diagnosis. Ask directly whether your family history meets the threshold for referral to a family history or genetics service, and whether you should start surveillance earlier than the screening programme would invite you.

If you have already had genetic testing in the family, bring that information too. A known pathogenic variant in a relative changes the conversation entirely, because you can be tested for that specific variant.