Fecal occult blood test (FOBT) is a test that uses a chemical reaction to detect the presence of small amounts of blood in the stool. FOBT may be helpful to screen or assess a number of conditions such as colorectal cancer, hemorrhoids, anal fissures, colon polyps, peptic ulcers, anemia, ulcerative colitis, or Crohn's disease.
This test is recommended every 1 to 2 years for people over the age of 50 to screen for colorectal cancer. More frequent testing may be needed for people who are at higher risk. Your doctor will determine if this test is required for you and how often you should take it.
Risks and precautions
FOBT is a very safe test. Be sure to follow the instructions provided and wash your hands after collecting stool samples.
Before the test
It is important that you fully understand what the test involves beforehand. Ask your doctor to explain the risks, benefits, and drawbacks of the test, and don't be shy to probe further until you are comfortable with your doctor's responses.
The test often requires three separate samples increase its chances of locating blood in the stool. Some foods may lead to a false test result. Therefore, you should avoid eating the following items 2 to 3 days before the test:
- bean sprouts
- iron supplements
- red meat
It is important to avoid conducting this test during your menstrual period or active bleeding from hemorrhoids.
Some medications, such as iron supplements, vitamin C supplements, acetylsalicylic acid (aspirin), and nonsteroidal anti-inflammatory drugs (NSAIDs; e.g., ibuprofen or naproxen), can cause a false test result. Avoid these medications for 2 to 3 days before the test.
If you are taking any prescription or over-the-counter (non-prescription) medications, supplements, or herbal products, make sure you inform your doctor or pharmacist. Ask them whether it is necessary for you to stop taking any of these medications and products before the test. It is also important to tell them if you have allergies to certain medications or have certain medical conditions.