What are the first signs of bowel cancer?

A change may involve constipation, diarrhoea, narrower stools, or a feeling that the bowel has not emptied. Blood can be bright red or make stools look dark. Tiredness may result from gradual blood loss, while weight loss can reflect reduced appetite or illness. These signs also occur with conditions that are not cancer, so a symptom does not identify its cause by itself.

Book a medical appointment when a bowel change, bleeding, fatigue, or weight loss persists or keeps returning. Bring a note of when it began, stool changes, visible blood, pain, appetite, and family history. A clinician may recommend tests such as colonoscopy, which allows the bowel lining to be examined and sampled when needed.

Seek urgent help for heavy rectal bleeding, black tar-like stools, severe abdominal pain, repeated vomiting, a swollen abdomen, or inability to pass stool or gas. Prompt assessment is also appropriate for ongoing rectal bleeding or unexplained weight loss, even when discomfort is mild.

Ask which tests fit your symptoms, whether colonoscopy is needed, and whether family history changes the assessment. If bowel cancer is diagnosed, ask how genomic tumour profiling may guide options and whether surgery, radiotherapy, or other treatment is relevant.