Blood Tests for Bowel Cancer

Blood tests may be used during bowel cancer investigation, diagnosis, treatment planning and follow-up. A blood test alone usually cannot diagnose bowel cancer, but it can give doctors important information about general health, anaemia, liver function, kidney function and treatment readiness.

This article is for general information only. Your doctor or healthcare team can explain which blood tests are needed in your situation and what the results mean.

Why Blood Tests May Be Done

Blood tests can help doctors understand whether symptoms may be linked with anaemia, infection, inflammation or other health problems. They may also help check whether a person is fit for surgery, chemotherapy or scans using contrast dye.

Blood tests are usually used together with other tests such as stool tests, colonoscopy, biopsy or scans.

Full Blood Count

A full blood count can check red blood cells, white blood cells and platelets. It may show anaemia, which can sometimes happen when there is ongoing bleeding from the bowel.

Anaemia does not always mean bowel cancer, but it may need further investigation if it is unexplained.

Liver and Kidney Function Tests

Liver function tests may be used because bowel cancer can sometimes spread to the liver. Kidney function tests can help doctors decide whether certain medicines or contrast scans are safe.

For more information about scans, read our CT Scan for Bowel Cancer and MRI Scan for Bowel Cancer articles.

CEA Blood Test

CEA is a tumour marker that may be checked in some people with bowel cancer. It can help with monitoring in selected cases, but it is not perfect and should not be interpreted alone.

For more detail, read our CEA Blood Test for Bowel Cancer guide.

Blood Tests and Diagnosis

Blood tests can support the investigation process, but bowel cancer diagnosis usually needs tests that examine the bowel or tissue directly, such as colonoscopy and biopsy.

For a wider overview, visit our Testing for Bowel Cancer article.

Final Thoughts

Blood tests can provide useful information during bowel cancer care, but they are only one part of assessment. Ask your doctor which tests were done, what the results mean and whether further tests are needed.