Stool test results: what a positive or negative result means
A positive FIT, guaiac or Cologuard result does not mean you have cancer. It means a colonoscopy is needed to find out why, and screening only works if that colonoscopy happens. A negative result means you repeat the test on schedule. Your doctor explains your result and decides what comes next. (ACS, 2026) (USPSTF, 2021)
A positive result
- FIT or guaiac test (gFOBT): hidden blood was found. Blood in the stool can come from cancer or polyps, but also from ulcers, hemorrhoids or other conditions. (ACS, 2026) The guaiac test cannot tell whether the blood came from the colon or higher up, such as the stomach; FIT is less likely to react to bleeding from the upper digestive tract. (ACS, 2026)
- Stool DNA test (such as Cologuard): the test found DNA changes, blood, or both. It also contains a FIT. (ACS, 2026)
- Either way, the next step is a colonoscopy. (ACS, 2026) (USPSTF, 2021)
Why a colonoscopy comes next, and how soon
The USPSTF says positive results on stool tests require a follow-up colonoscopy for screening to deliver its benefit. (USPSTF, 2021) The American Cancer Society says any abnormal result from a test other than colonoscopy should be followed up with a timely colonoscopy, rather than another stool test. (ACS, 2026)
On timing, one large study of about 70,000 people aged 50 to 70 with a positive FIT at Kaiser Permanente in California found no clear difference in cancer risk when the colonoscopy was done within 9 months compared with 8 to 30 days. Waiting 10 months or longer was linked to a higher chance of colorectal cancer and of a later stage at diagnosis. The authors say more research is needed to know whether the delay itself caused this. (Corley et al., JAMA 2017) Your doctor sets the date; if you have not heard about scheduling, ask.
What the colonoscopy finds then decides your next date. If polyps are removed, see colonoscopy after polyps.
False positives
All stool tests can give a false-positive result: a positive test when no cancer is there. (ACS, 2026) A false positive can cause worry and leads to more tests, such as a colonoscopy, which have their own risks. (NCI, 2025) In the studies the USPSTF reviewed, FIT came back negative for about 94 in 100 people who did not have colorectal cancer, and stool DNA-FIT for about 84 in 100. The USPSTF says stool DNA-FIT gives more false positives than FIT, and so more follow-up colonoscopies. (USPSTF, 2021)
For the guaiac test, the American Cancer Society says NSAIDs such as ibuprofen, naproxen or aspirin in the 7 days before can cause bleeding and a false positive, and red meat in the 3 days before can make the test positive. People who take these medicines daily should not stop them for the test without talking to their doctor. FIT has no food or medicine limits. (ACS, 2026)
If the colonoscopy after a positive stool DNA test is normal, the USPSTF says there is not enough evidence yet on how those people should be followed. (USPSTF, 2021) Your doctor advises you. More: false positives and overdiagnosis.
A negative result, and when to repeat
A negative result means the test found no sign of cancer this time, but stool tests can miss many polyps and some cancers, which is why they are repeated. (ACS, 2026) A false-negative result can also lead someone to delay seeing a doctor even with symptoms. (NCI, 2025) If you have symptoms such as blood in your stool, see your doctor rather than waiting for the next test.
The bodies differ on how often to repeat a stool DNA test. The USPSTF says every 1 to 3 years and notes that modeling found every 3 years less efficient than every 1 or 2 years. (USPSTF, 2021) The American Cancer Society says every 3 years, (ACS, 2026) and Medicare covers one every 3 years. (Medicare.gov)
| Test | Looks for | USPSTF | American Cancer Society | Medicare covers |
|---|---|---|---|---|
| FIT (fecal immunochemical test) | Hidden blood in the stool (ACS, 2026) | Every year (USPSTF, 2021) | Every year (ACS, 2026) | Once every 12 months (Medicare.gov) |
| High-sensitivity gFOBT (guaiac test) | Hidden blood in the stool (ACS, 2026) | Every year (USPSTF, 2021) | Every year (ACS, 2026) | Once every 12 months (Medicare.gov) |
| Stool DNA test (such as Cologuard) | DNA changes and blood (ACS, 2026) | Every 1 to 3 years (USPSTF, 2021) | Every 3 years (ACS, 2026) | Every 3 years (Medicare.gov) |
What the follow-up colonoscopy costs
Medicare Part B covers a stool blood test once every 12 months from age 45 with a referral, and a stool DNA test every 3 years for people 45 to 85 with no symptoms and average risk. After a positive result on either, Medicare also covers a follow-up colonoscopy as a screening test. (Medicare.gov) (Medicare.gov) You pay nothing for the screening if your provider accepts assignment; if a polyp or other tissue is removed, you pay 15% of the Medicare-approved amount for your provider's services, and a 15% facility coinsurance in a hospital outpatient setting or surgery center. (Medicare.gov) For private plans, federal rules count the follow-up colonoscopy as part of screening; details are on colorectal tests compared.
Questions people ask
What does a positive FIT test mean?
Hidden blood was found in your stool. It does not mean you have cancer. Blood can come from polyps or cancer, but also from ulcers, hemorrhoids or other conditions. A colonoscopy is needed to find the cause. (ACS, 2026)
What happens after a positive Cologuard test?
A colonoscopy. The American Cancer Society says a positive stool DNA test, whether it found DNA changes or blood, means a colonoscopy needs to be done, and the USPSTF says screening only works if that follow-up happens. (ACS, 2026) (USPSTF, 2021)
Can I just repeat the stool test instead?
The American Cancer Society says any abnormal result from a test other than colonoscopy should be followed up with a timely colonoscopy. Ask your doctor before choosing anything else. (ACS, 2026)
How soon should I have the colonoscopy?
Soon. The American Cancer Society calls for a timely colonoscopy. In one large study of people with a positive FIT, waiting 10 months or longer was linked to a higher chance of colorectal cancer and of a later stage at diagnosis than having it within 8 to 30 days. Your doctor sets the date. (ACS, 2026) (Corley et al., JAMA 2017)
Will Medicare pay for the colonoscopy after a positive stool test?
Yes. Medicare covers a follow-up colonoscopy after a positive stool test as a screening test, and you pay nothing for the screening if your provider accepts assignment. If a polyp is removed, you pay 15% of the Medicare-approved amount for the provider, and a facility coinsurance may apply. (Medicare.gov) (Medicare.gov) (Medicare.gov)