FIT Test for Bowel Cancer: What It Is, Why It Matters & What to Do If It's Positive
Bowel cancer — also known as colorectal cancer — is one of the most common types of cancer in the UK. But when caught early, it’s also one of the most treatable. That’s where the FIT test comes in.
At Optimum Health Screening, we offer Faecal Immunochemical Testing (FIT) as part of our Male Cancer Health Check — giving you a convenient and effective way to check for early signs of bowel cancer.
What Is a FIT Test?
The FIT test (Faecal Immunochemical Test) is a simple stool test that checks for tiny traces of blood in your poo — blood that is not visible to the naked eye.
The presence of blood in the stool can indicate a number of gastrointestinal issues, including bowel cancer, polyps, or inflammation.
The test is quick, non-invasive, and can be done in the privacy of your own home. It works by detecting human haemoglobin (a component of blood) in faeces, and is more specific and sensitive than older stool tests like the traditional guaiac Faecal Occult Blood Test (gFOBT).
Why Is the FIT Test Important?
Early detection saves lives: Bowel cancer often develops with no symptoms in the early stages.
Non-invasive: No need for hospital visits or complex procedures.
Simple and fast: One small stool sample is all that's needed.
Accurate: FIT is more precise than traditional screening tests.
Regular screening with a FIT test can help detect problems before symptoms even appear, offering the best chance for early treatment and recovery.
What Causes Bleeding in the Gastrointestinal Tract?
A positive FIT result means blood has been detected in your stool. While this may sound alarming, it doesn’t automatically mean you have cancer. Other common causes include:
Haemorrhoids (piles): Swollen veins in the rectum that can bleed during bowel movements.
Anal fissures: Small tears in the skin around the anus.
Diverticulosis: Small bulges or pockets in the bowel wall that can become inflamed or bleed.
Inflammatory bowel disease (IBD): Conditions like Crohn’s disease or ulcerative colitis that cause chronic inflammation.
Polyps: Non-cancerous growths that can occasionally bleed and may develop into cancer over time.
Gastrointestinal infections: Certain infections may irritate the bowel lining, causing bleeding.
What Is Bowel Cancer?
Bowel cancer, or colorectal cancer, occurs in the large intestine (colon) or rectum. It often begins as benign polyps that can, over time, become cancerous.
Symptoms of Bowel Cancer Include:
Persistent changes in bowel habits (diarrhoea or constipation)
Blood in the stool (sometimes not visible)
Unexplained weight loss
Abdominal pain or discomfort
Feeling that your bowel doesn't empty fully
Fatigue or weakness
However, many people with early bowel cancer experience no symptoms at all — which is why regular testing is crucial.
How Treatable Is Bowel Cancer?
When diagnosed early, bowel cancer is highly treatable. According to Cancer Research UK, over 90% of people survive bowel cancer for five years or more if it’s diagnosed at the earliest stage.
That’s why screening with a FIT test is so important — it can catch cancer before symptoms appear.
What If the FIT Test Is Positive?
If your result is positive (Faecal occult blood (FIT) >10 μg Hb/g faeces), this does not necessarily mean you have bowel cancer.
There are many possible causes of gastrointestinal bleeding. However, a positive test means that further investigations are needed to find the source.
Your GP will likely refer you urgently for additional tests, which may include:
Colonoscopy – A camera examination of your bowel
Flexible sigmoidoscopy – A look at the lower part of your colon
CT colonography – A virtual colonoscopy using CT imaging
These procedures help locate the bleeding source and determine whether further treatment is necessary.
What If the FIT Test Is Negative?
If your result is negative (Faecal occult blood (FIT) <10 μg Hb/g faeces), it is very unlikely you have bowel cancer. You do not need an urgent referral for suspected bowel cancer.
However, if you continue to have symptoms or your GP has concerns, they may request additional tests or specialist advice. This will follow local clinical guidelines.
How Likely Is It to Be Cancer If the FIT Test Is Positive?
Studies show that between 7% and 16% of people who test positive for FIT have bowel cancer diagnosed following further investigations. The risk increases with the amount of blood detected and the presence of symptoms.
So while most people with a positive result do not have cancer, it’s essential to follow up quickly to rule it out.
How Accurate Is the FIT Test?
The FIT test is currently one of the most accurate non-invasive screening tools available:
Sensitivity: ~79% (ability to detect cancer)
Specificity: ~94% (ability to rule out those without cancer)
It is significantly more reliable than older occult blood tests and can detect even low levels of blood that may otherwise be missed.
How Often Should You Have a FIT Test?
It’s recommended that individuals aged 40 and over — especially men — consider a yearly FIT test, even if they feel well.
At Optimum Health Screening, the FIT test is included in our Male Cancer Health Check, designed to screen for multiple types of cancer in one convenient package.
Book Your FIT Test Today
Bowel cancer is preventable and treatable — but only if caught early. Whether you’re experiencing symptoms or simply want peace of mind, the FIT test is a powerful tool in protecting your long-term health.
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