What should you know about a false-negative FIT test?

A false-negative FIT test means the sample did not detect blood even though bleeding may still be present. FIT checks for hidden blood in one bowel sample, so the result is a screening result rather than a complete assessment of bowel health.

Blood may not be evenly distributed through stool, and a sample may not contain blood if bleeding is intermittent. Collection technique, an inadequate sample, or bleeding from a source that FIT does not capture well can also affect the result. A negative test therefore does not explain ongoing bowel symptoms by itself.

A person with ulcerative colitis may need a planned monitoring approach that is different from routine screening. The result should be interpreted alongside age, symptoms, personal history, and family history.

Check whether the sample was collected and returned as instructed, and keep a record of symptoms such as visible blood, a persistent change in bowel habit, abdominal pain, or unexplained weight loss. Contact a GP or screening service if symptoms continue, return, or differ from the reason you were tested. They may review the result and decide whether examination, blood tests, repeat testing, or another bowel investigation is appropriate.

Seek urgent medical help for heavy or repeated rectal bleeding, black tar-like stool, fainting, severe abdominal pain, or marked weakness. These features can indicate significant bleeding or another urgent bowel problem, even after a negative FIT result.

Ask: Could my symptoms need assessment despite the FIT result? Was the sample suitable for analysis? Do my medical or family history change the next step? Should I have a blood count or another bowel investigation? When should I repeat screening?