The short answer
This page compares the three kinds of home stool tests used to screen for colorectal cancer. It is general education, not individual medical advice.
Stool tests are done at home with no bowel prep. They look for hidden blood, and some also look for changed DNA.
CDC says FIT and gFOBT are done once a year. The USPSTF (2021 final recommendation) lists the stool DNA-FIT test every 1 to 3 years.
A positive stool test is not a diagnosis. It means you need a colonoscopy to finish the screening.
The best test is the one you will actually do, on schedule.
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The whole article, with every detail and caution.
This page is for anyone choosing a home stool test for colorectal cancer screening, or trying to understand the kit that came in the mail. It compares the three types, how often you repeat them, and what a positive result means.
Who stool tests are for
The U.S. Preventive Services Task Force (USPSTF) final recommendation from May 2021 advises screening for adults 45 to 75 at average risk. For ages 76 to 85, it says the choice should be made one person at a time. Stool tests are one of several accepted options. Colonoscopy is another. Our colorectal cancer screening page covers all of them.
Stool tests are for people with no symptoms. If you have bleeding from the rectum, blood in your stool, or a change in bowel habits that does not go away, talk to your care team. A home test is not the right tool for checking symptoms.
The three types of stool test
All three are done at home. There is no bowel prep and no sedation. You collect a sample and send it to a lab.
FIT (fecal immunochemical test). CDC says FIT uses antibodies to find hidden blood in the stool. You use a stick or brush to collect a small sample. It is done once a year.
gFOBT (guaiac-based fecal occult blood test). This older test uses a chemical called guaiac to find hidden blood. CDC says it is also done once a year, in the same way. Some gFOBT kits ask you to avoid certain foods or medicines first, so read the kit.
Stool DNA test (sDNA-FIT, or FIT-DNA). This test combines a FIT with a test that looks for changed DNA in the stool. Cologuard is one brand name. CDC explains that you collect a whole bowel movement and send it to a lab. CDC lists it as once every 3 years. The USPSTF lists it as every 1 to 3 years.
How they compare
| FIT | gFOBT | Stool DNA (sDNA-FIT) | |
|---|---|---|---|
| What it looks for | Hidden blood | Hidden blood | Hidden blood and changed DNA |
| Sample | Small sample | Small sample | Whole bowel movement |
| How often | Every year | Every year | Every 1 to 3 years |
| If positive | Colonoscopy | Colonoscopy | Colonoscopy |
A stool test that needs repeating every year only works if you do it every year. When you choose, think about which test you are most likely to keep up with.
If your result is positive
A positive result does not mean you have cancer. It means something needs a closer look. CDC states that a colonoscopy is needed to complete the screening process. During it, doctors can look at the whole colon and remove polyps.
Many positive results turn out to be polyps or other causes. What matters is to follow through. Skipping the colonoscopy after a positive test undoes the point of screening. Our page on what happens after a positive at-home stool test walks through the next steps.
If your result is negative
A negative result is good news, but no test is perfect. Keep to your schedule for the next test. Talk to your care team if new symptoms appear before then.
Sources
Common questions
What is the difference between FIT and Cologuard?
FIT looks only for hidden blood in a small stool sample, using antibodies. Cologuard is a brand of stool DNA test, called sDNA-FIT or FIT-DNA. CDC explains that it combines a FIT with a test for changed DNA, and you collect a whole bowel movement. FIT is done every year. CDC lists FIT-DNA every 3 years, and the USPSTF lists it every 1 to 3 years.
Do I need to prepare for a stool test?
There is no bowel prep and no sedation. Follow the instructions in your kit exactly. Some guaiac-based tests (gFOBT) have food or medicine limits before the test, so read the kit or ask your care team.
What happens if my stool test is positive?
CDC says a colonoscopy is needed to complete the screening process. Many positive results turn out to be polyps or harmless causes, but the follow-up colonoscopy matters. Without it, the screening is not finished.
Are stool tests right if I have a higher risk?
Stool tests are for people at average risk with no symptoms. If you have a family history of colorectal cancer, an inherited condition, or bowel symptoms such as bleeding, talk to your care team about which test fits you.
Questions to ask your doctor
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Your next step
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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