Blood and lab tests
What Does Fecal Occult Blood Mean on a Stool Test?
Fecal occult blood · say it: FEE-kul uh-KULT bludAlso written: faecal occult blood, FOBT, FIT, faecal immunochemical test, hidden blood in stool
Short answer
Fecal occult blood is blood in a stool sample that is too small to see with the eye but can be found with a lab test.
What it means
Occult means hidden. A fecal occult blood test looks for tiny amounts of blood in a stool sample that you would not notice yourself. Older tests (guaiac tests) detect a chemical reaction, while the newer fecal immunochemical test, or FIT, detects human blood protein using antibodies.
The test is widely used in bowel cancer screening programmes and also to look into symptoms like a change in bowel habit or anemia. Bleeding anywhere in the gut can give a positive result. A positive result is a signal to look further, usually with a camera test of the bowel (colonoscopy), rather than a diagnosis on its own.
This is different from seeing blood in the toilet or on the paper, which you should tell a doctor about whatever a stool test shows. It is also different from a stool test for germs or parasites.
Where you may see it
- Bowel cancer screening result letters
- Lab reports headed 'FIT' or 'Faecal occult blood'
- GP or primary care referral letters for colonoscopy
- Home screening kit instructions
📄 How it looks on a report
Faecal immunochemical test (FIT): POSITIVE. Referral for colonoscopy recommended.
🙅 What it does not mean
- A positive result does not mean you have cancer. Hidden blood can come from polyps, piles (hemorrhoids), inflammation, ulcers and other causes.
- A negative result does not rule out every bowel problem, because some growths do not bleed every day. Screening programmes repeat the test at set intervals for this reason.
- A FIT result is not changed by red meat or most foods, unlike some older guaiac tests, so your lab's instructions about diet depend on which test you had.
🗒️ Questions to ask your doctor
🧾 Reports where you will see “Fecal occult blood”
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🔗 Read more from trusted sources
- “Fecal occult blood” on MedlinePlus ↗
US National Library of Medicine
- MedlinePlus lab test guides ↗
US National Library of Medicine
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General information about a medical word, not advice about your own results. Ask the clinician who ordered the test what it means for you.