Stool Occult Blood Test (Fecal Immunochemical Test, FIT)

This test measures the level of a specific substance in your body, such as a hormone, protein, or other marker, that helps your doctor evaluate how well certain organs and body systems are working.

The FIT test detects microscopic amounts of blood in your stool that may not be visible to the naked eye. Blood can come from various parts of the digestive system, including the esophagus, stomach, colon, or rectum. This test uses antibodies to identify hemoglobin, the protein in red blood cells, which appears in stool when bleeding occurs.

Your doctor orders this test to help diagnose a health condition, find the cause of symptoms you may be having, check how well a treatment is working, or monitor an existing condition over time.

Doctors may recommend this test to screen for colorectal cancer or other conditions causing internal bleeding, such as hemorrhoids, polyps, or inflammatory bowel disease. It’s often part of routine screening, especially for adults over 50, or if you have symptoms like unexplained weight loss, persistent abdominal pain, or changes in bowel habits.

The test is performed by collecting a small sample, usually a blood draw from a vein in your arm or a urine sample, which is then sent to a laboratory for analysis. The process takes only a few minutes and causes minimal discomfort.

You’ll collect a sample of your stool using a provided collection kit, typically over a 3-day period. The sample is then sent to a lab for analysis. The test is non-invasive and doesn’t require fasting or special preparation beyond following the kit instructions.

Your results show whether your measured value falls inside or outside the normal range. An abnormal value does not always mean illness, but it may prompt your doctor to order follow-up testing or adjust your care plan.

A positive result means there is detectable blood in your stool, which may prompt further testing (like a colonoscopy) to find the cause. A negative result doesn’t rule out bleeding entirely, so follow-up may still be needed if you have symptoms. Results are qualitative (positive or negative) and not tied to specific numeric ranges.