The Fecal Occult Blood Immunoassay (iFOBT or FIT test) is one of the primary recommended screening tools for colorectal cancer in adults 45 and older. It detects tiny amounts of blood in a stool sample that are invisible to the naked eye — blood that can indicate polyps, early-stage colorectal cancer, or other sources of gastrointestinal bleeding before any symptoms develop.
Immunoassay vs. Guaiac — what’s the difference? There are two types of fecal occult blood tests. The older guaiac-based test (gFOBT) uses a chemical reaction and can be affected by diet, medications, and animal blood in food. The immunoassay version (iFOBT or FIT) uses antibodies that react specifically to human hemoglobin — making it significantly more accurate, with no dietary restrictions required before testing. This is the immunoassay version.
Also Known As: FOBT, Stool Occult Blood Test, Occult blood test, Hemoccult test, Immunochemical FOBT, Guaiac Smear Test, and Stool Guaiac Test
Purpose of the Fecal Occult Blood Test
The fecal occult blood test is performed as part of a health and wellness screening or to confirm gastrointestinal bleeding as part of early detection for colorectal cancer, inflammatory bowel disease (IBD), and other related conditions.
Tests Included:
What does the Fecal Occult Lab Test measure?
A fecal occult blood immunoassay detects blood in the stool that cannot be seen with the naked eye, known as occult blood. Using a fecal sample, blood is confirmed by determining the presence of a chemical reaction upon the introduction of specific substances, particularly guaiac and hydrogen peroxide.
Who Should Take a Screening Test for Fecal Occult?
Individuals at risk of colorectal cancer should take a fecal occult blood test as part of their annual screening or cancer work-up. These include people over 45 years old and those with a family history of cancer.
In addition, people planning to undergo weight loss should also consider adding the fecal occult lab test in their blood workup. Depending on the symptoms, physicians may also recommend the test to confirm other gastrointestinal disorders like Celiac disease, polyposis, and IBD.
Recommended screening frequency: The American Cancer Society recommends annual fecal occult blood or FIT testing beginning at age 45 for average-risk adults. People with a personal or family history of colorectal cancer or polyps, or with inflammatory bowel disease, may need to begin screening earlier and at more frequent intervals — discuss timing with your physician.
Important ordering note: If ordering this test alongside other tests, please place it as a separate order. The fecal sample must be collected and submitted before other lab work is processed. This ensures accurate results and proper sample handling.
Fecal Occult Blood Immunoassay Test Preparation
No special preparation, specifically drug or dietary restrictions, are generally required prior to the test. Results of this test are not affected by dietary peroxidases, animal blood, or vitamin C. If you have other questions or concerns, consult with your healthcare provider first.
Stool Occult Blood Test Results
Fecal occult blood immunoassay test results indicate whether or not blood is detected in your sample. Typically, it’s confirmatory, indicating whether the result is positive or negative.
Where Can I Get a Fecal Occult Blood Test Done Near Me?
Take the screening test for fecal occult at Personalabs. Simply follow these steps.
Step 1: Visit our website’s lab tests section. Then, order the test and download the lab test order, serving as a doctor’s order for your lab work.
Step 2: Choose a nearby lab using our lab locator.
Step 3: Get your blood drawn at the lab of your choice.
Step 4: Expect the lab test results within 2-10 business days in your Personalabs account.
For an exact turnaround time for results, please contact us at 1-888-438-5227.
*If ordering additional tests, please place a separate order as Fecal Occult Blood Test sample must be given first.
Estimated Turn Around For Results:
2-10 Business Days
For an exact turnaround time for results, please contact us at Personalabs and we will contact the lab on your behalf as turnaround times vary depending on testing location or lab testing provider.
Frequently Asked Questions
What is the fecal occult blood immunoassay test used for? This test screens for hidden (occult) blood in a stool sample that cannot be seen with the naked eye. It is used as a first-line colorectal cancer screening tool, to investigate gastrointestinal bleeding, and to support diagnosis of conditions like inflammatory bowel disease, polyps, and other GI disorders.
Do I need to restrict my diet before this test? No. Unlike the older guaiac-based fecal occult blood test, the immunoassay version (iFOBT/FIT) uses antibodies that react specifically to human hemoglobin and is not affected by dietary factors, animal blood in food, or vitamin C. No dietary restrictions are required.
What does a positive fecal occult blood test mean? A positive result means blood was detected in the stool sample. This does not automatically mean cancer — common causes of a positive result include hemorrhoids, anal fissures, polyps, inflammatory bowel disease, and ulcers, in addition to colorectal cancer. A positive result should always be followed up with a physician for further evaluation, typically a colonoscopy.
Who should get an annual fecal occult blood test? The American Cancer Society recommends annual FOBT/FIT screening starting at age 45 for average-risk adults. People with a personal or family history of colorectal cancer or polyps, or with IBD, may need to begin earlier and test more frequently.
How long does it take to get results? Results are typically available within 2–10 business days through your Personalabs account. Contact us at (888) GET-LABS for location-specific turnaround times.
