bowel blood test explained

Overview

A bowel blood test (also called a faecal occult blood test or FOBT) is a simple home test that checks for tiny amounts of blood in your stool (poo). Even small amounts of blood that you cannot see can be a sign of bowel problems such as polyps (growths that may become cancer) or bowel cancer. The test involves collecting a small sample of your stool and sending it to a lab for analysis. It is not a blood test – it is a stool test.

Bowel cancer is common – it is the fourth most common cancer in the UK. The bowel blood test is a standard, widely used screening test to detect it early.

The test is mainly offered to adults aged 60 to 74 in many countries. It may also be offered to younger people if they have a strong family history of bowel cancer or certain conditions that increase risk.

Symptoms

Common symptoms

• A change in your normal bowel habits that lasts longer than a few weeks (for example, going more or less often, or having looser or more runny poo).
• Blood in your poo – either obvious (bright red or dark) or hidden (only found by the test).
• Unexplained weight loss or tiredness (anaemia).
• A feeling that you need to go to the toilet even when your bowel is empty (tenesmus).

Symptoms in children

• In children, visible blood in the stool is more often caused by constipation, anal fissures (small tears), allergies, or infections – not bowel cancer. The bowel blood test is not usually used for children.

Symptoms in older adults

• Blood in the stool in older adults can have many causes, including haemorrhoids, diverticulosis, polyps, or cancer. The test helps find the cause early.

Causes

Main causes

• Polyps (non‑cancerous growths on the lining of the bowel that can sometimes become cancerous).
• Bowel cancer (colorectal cancer).
• Haemorrhoids (swollen veins in the back passage).
• Anal fissures (small tears in the skin around the anus).
• Diverticular disease (small pouches in the bowel wall that can bleed).
• Inflammatory bowel disease (Crohn’s disease or ulcerative colitis).

Risk factors

• Age – risk increases after 50.
• A family history of bowel cancer or polyps.
• A personal history of polyps or bowel cancer.
• Long‑standing inflammatory bowel disease (Crohn’s or ulcerative colitis).
• Being overweight or having a diet high in red or processed meats.
• Smoking and drinking alcohol heavily.

When to see a doctor

See a doctor urgently if:

• If you notice any blood in your stool, especially if you are over 50.
• If you have a persistent change in bowel habit that lasts more than three weeks.
• If you have been invited for bowel blood test screening and have not done it – or if you missed your last test.

Book a routine appointment if:

• When you receive an invitation from your national screening programme (usually for people aged 60‑74).
• If you have no symptoms but are at higher risk (for example, family history), ask your doctor about earlier or more frequent screening.

Diagnosis

The bowel blood test is done at home. You will receive a kit with instructions, a small container to collect a stool sample, and a card or tube to place the sample. After collecting the sample, you seal it and send it to a laboratory (using a prepaid envelope). The lab tests the sample for hidden blood. Results come back within a few weeks – usually by letter.

Tests that may be done

• Faecal occult blood test (FOBT) or faecal immunochemical test (FIT) – the home stool test described above.
• Colonoscopy – a procedure where a thin, flexible tube with a camera is used to look at the inside of your bowel. This is usually done if the stool test is positive.
• Flexible sigmoidoscopy – a shorter version of a colonoscopy that looks at the lower part of the bowel.

What to expect at your appointment

If your bowel blood test is positive, your doctor will arrange a colonoscopy. You will be given instructions on how to prepare (usually a special diet and laxatives to empty your bowel). The procedure itself takes about 30‑45 minutes and you may be given a sedative to help you relax. You will be told the results before you leave or soon after.

Treatment

Treatment depends on what the bowel blood test and follow‑up tests find. If the cause is a polyp, it can often be removed during the colonoscopy. If cancer is found, treatment may involve surgery, radiotherapy, or chemotherapy. The earlier the problem is found, the simpler and more effective treatment is likely to be.

Self-care at home

• Follow a healthy diet with plenty of fibre (whole grains, fruits, vegetables) and limit red and processed meats.
• Drink plenty of water and stay physically active.
• Do not ignore symptoms – seek medical advice promptly.

Medical treatments

Treatment approaches for bowel problems found by the test may include removing polyps during colonoscopy (polypectomy), surgery to remove part of the bowel, radiotherapy to shrink tumours, and chemotherapy to kill cancer cells. Your healthcare team will discuss the best plan with you. Specific medicines, such as targeted therapies, may be used in some cases but should only be prescribed by your doctor.

When is surgery considered?

Surgery is often needed if bowel cancer is found. The operation removes the cancerous part of the bowel and nearby lymph nodes. In many cases, the remaining bowel can be joined back together and you will not need a permanent stoma (bag).

Living with this condition

After a positive bowel blood test and any necessary treatment, most people return to their normal activities. You may need regular follow‑up tests (colonoscopies every few years) to check for new polyps. If you have had cancer, you will have a follow‑up care plan.

Lifestyle tips

• Eat a balanced diet rich in fibre and low in red/processed meat.
• Stay physically active – aim for at least 30 minutes of moderate exercise most days.
• Avoid smoking and limit alcohol.
• Attend all recommended follow‑up appointments and screening tests.

Diet and exercise

A diet high in fibre from fruits, vegetables, and whole grains may help prevent polyps and keep your bowel healthy. Regular exercise helps maintain a healthy weight and lowers your risk of bowel problems. If you have had treatment, your doctor or dietitian can give you personalised advice, especially if your bowel habits have changed.

Mental health and emotional wellbeing

Waiting for test results or facing a cancer diagnosis can be very worrying. It is normal to feel anxious, scared, or stressed. Talk to your doctor, a counsellor, or a support group. You do not have to go through it alone. If you feel overwhelmed, reach out for help.

Prevention

You cannot prevent all bowel problems, but you can reduce your risk by eating a healthy diet, staying active, not smoking, and limiting alcohol. The bowel blood test itself is a prevention tool – it finds polyps before they become cancer.

Screening programmes

Regular screening with the bowel blood test (every two years for those aged 60‑74 in the UK) is the best way to detect bowel cancer early. If you are at higher risk, your doctor may recommend starting screening earlier or having a colonoscopy instead.

Complications

If left untreated

• If a polyp that is found is not removed, it may slowly develop into cancer over years.
• If bowel cancer is not treated, it can grow into nearby tissues and spread to other parts of the body (metastasise), making it much harder to treat.
• Bleeding from a polyp or cancer can cause anaemia (low red blood cells), leading to tiredness and weakness.

Long-term outlook

The outlook for bowel problems found through screening is very good. When caught at an early stage, bowel cancer is highly treatable and most people survive. The bowel blood test is a simple way to give yourself the best chance of a positive outcome. If cancer is found later, treatments have improved greatly and many people still do well. Your doctor can give you a more personal outlook based on your situation.

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