Fecal occult blood test (FOBT/FIT): what the result means (iFOBT)
- Updated
- 2026-09-10
- Every number with its source
What the test is
A fecal occult blood test (FOBT; the immunochemical version is called iFOBT or FIT) detects small amounts of blood in stool that cannot be seen with the naked eye and that cause no noticeable symptoms. Two main types of method are used: the guaiac test, which detects the heme of blood by a chemical reaction, and the immunochemical test (iFOBT/FIT), which uses antibodies to detect human haemoglobin and is more sensitive and less dependent on the food eaten. Per MedlinePlus, this test is most often used as a screening tool for colon cancer in people who have no symptoms at all. It is also used when bleeding in the digestive tract is suspected, when the cause of anaemia is being established, or to tell inflammatory bowel disease from irritable bowel syndrome. A positive result means that blood is present, but it does not say from which part of the digestive tract it came or what caused it — further tests are needed for that.
A positive result
A positive (detected) result shows that there is blood in the stool, but this does not in itself mean cancer. The causes range from benign ones (haemorrhoids, ulcers of the digestive tract) to ones that need more urgent investigation (polyps, colon cancer). Per MedlinePlus, after a positive result a doctor usually recommends further tests, among them a colonoscopy.
| Group of causes | Examples | What to keep in mind |
|---|---|---|
| Benign causes | Haemorrhoids, ulcers of the digestive tract | A positive result does not in itself mean cancer, but it also does not say what caused the blood — further tests are needed for that |
| Causes that need more urgent investigation | Polyps, colon cancer | Per MedlinePlus, a doctor usually recommends further tests after a positive result, among them a colonoscopy |
When the test is done
- For colon cancer screening when there are no symptoms at all — usually in older people, under a screening programme
- When there is abdominal pain or a change in how the bowel works
- When the cause of anaemia is being established and a complete blood count has found a decreased haemoglobin or iron deficiency
- If you notice blood in your stool or black, tar-coloured stools, do not wait for this test — it is meant for blood that cannot be seen (MedlinePlus). Black or dark red stools are a reason to see a doctor urgently, and if bleeding does not stop or there is a lot of blood, call 112 (NHS)
- To tell inflammatory bowel disease from irritable bowel syndrome
How to prepare
- Some guaiac-based tests require avoiding non-steroidal anti-inflammatory drugs, large doses of vitamin C, red meat and certain raw fruit and vegetables (for example melons, broccoli, radishes, horseradish) before the test — your doctor or the laboratory will tell you about this
- Immunochemical (iFOBT/FIT) tests usually require no special preparation
- Talk to your doctor before stopping any medicine you take regularly
How the result is reported
The result of this test is most often reported as positive (blood detected) or negative; any numerical cut-off depends on the laboratory's method, and public sources give no common range, so no number is given here. You will find your laboratory's cut-off on your own result sheet, and the result is assessed by a doctor. A positive result means that blood is present in the stool, but it does not by itself say which part of the digestive tract it came from or what caused it, and it does not by itself mean cancer. Per MedlinePlus, after a positive result a doctor usually recommends further tests, among them a colonoscopy. One of the things a doctor also assesses is whether medicines or foods taken around the time of the test could have affected the result — non-steroidal anti-inflammatory drugs, vitamin C, red meat.
Possible causes of a positive result
- Polyps in the colon
- Haemorrhoids
- Diverticulosis
- Ulcers in the stomach or duodenum
- Ulcerative colitis or another inflammatory bowel disease
- Colon or rectal cancer
What to discuss with a doctor after a positive result
- A colonoscopy or another visual examination of the bowel, if the result is positive
- A complete blood count and iron markers, if anaemia due to bleeding is suspected
- An assessment of whether medicines or foods taken at the time of the test could have affected the result (non-steroidal anti-inflammatory drugs, vitamin C, red meat)
- A discussion with a doctor of any symptoms — abdominal pain, changes in bowel function, weight loss
- When to repeat the screening test, according to age and family history
The guaiac test and iFOBT (FIT)
The guaiac test detects blood by a chemical reaction and is sensitive to the effect of food and medicines, which is why certain products have to be avoided before it. The immunochemical test (iFOBT/FIT) uses antibodies to detect human haemoglobin, is more sensitive and usually requires no special preparation.
About Lithuania
Paying privately at the Medicina practica laboratory in Lithuania, the iFOBT test costs from €11 (September 2026 pricing). A family doctor can order the test free of charge under the screening programme or when there are indications.
Related pages
Related pages on this site: haemoglobin, ferritin, iron, CRP, the calprotectin stool test and CEA.
Full site in Lithuanian: proactiva.app
Frequently asked questions
›What is a fecal occult blood test?
It is a test that detects small amounts of blood in stool that cannot be seen with the naked eye. Per MedlinePlus, it is most often used as a screening tool for colon cancer in people without symptoms, and also when the cause of bleeding in the digestive tract or of anaemia is being established.
›Does a positive result mean cancer?
Not always. Per MedlinePlus, a positive result shows that there is bleeding in the digestive tract, but the cause of it is often benign — haemorrhoids, polyps, ulcers or diverticulosis. To establish the exact cause, further tests are needed, most often a colonoscopy.
›What is the difference between the guaiac test and iFOBT (FIT)?
The guaiac test detects blood by a chemical reaction and is sensitive to the effect of food and medicines, so certain products have to be avoided before it. The immunochemical test (iFOBT/FIT) uses antibodies to detect human haemoglobin, is more sensitive and usually requires no special preparation.
›Is any special preparation needed before the test?
It depends on the type of test. Some guaiac-based tests require avoiding non-steroidal anti-inflammatory drugs, large doses of vitamin C, red meat and some raw vegetables before the test. Immunochemical (iFOBT/FIT) tests usually require no such preparation — check with your laboratory.
›Are there any risks in having this test?
Per MedlinePlus, there are no known risks in having a fecal occult blood test — the sample is collected at home with a special kit, and no invasive procedures are needed.
›How much does this test cost in Lithuania?
At the Medicina practica laboratory, the iFOBT test costs from €11 (September 2026 pricing). A family doctor can order the test free of charge under the screening programme or when there are indications.
Sources
Related markers
This site is not an emergency service. If severe chest or head pain, breathlessness, confusion, difficulty speaking, heavy bleeding or another acute problem has come on suddenly — do not wait for tests, call 112.
This information is not a diagnosis and does not replace a consultation with a doctor. Reference ranges depend on the laboratory, your age and sex — always compare your result with the range printed on your own report.