Colorectal screening tests compared

For adults 45 to 75 at average risk, the USPSTF lists several tests and does not name one as best. They differ in where they are done, the prep, how often you repeat them and what happens after an abnormal result. Here they are side by side, with what insurance and Medicare pay.

The USPSTF says the tests differ in ways that can help or get in the way of actually having them done, such as where they are done, prep, sedation and follow-up. Its list: a high-sensitivity guaiac stool test (gFOBT) or FIT every year, stool DNA-FIT every 1 to 3 years, CT colonography every 5 years, flexible sigmoidoscopy every 5 years (or every 10 years with a FIT every year), or colonoscopy every 10 years. (USPSTF, 2021)

Side by side

Colorectal cancer screening tests compared by where they are done, prep, sedation, interval and next step after an abnormal result
Test	Where and how	Prep and sedation	How often (USPSTF)	If abnormal
FIT (fecal immunochemical test)	Stool sample at home; looks for hidden blood	No bowel prep, no diet or medicine changes (ACS, 2026)	Every year (USPSTF, 2021)	Colonoscopy
High-sensitivity gFOBT	Stool samples at home; looks for hidden blood	No bowel prep; unlike FIT, some food and medicine limits beforehand (ACS, 2026)	Every year (USPSTF, 2021)	Colonoscopy
Stool DNA-FIT (Cologuard)	A whole bowel movement collected at home with a mailed kit; looks for DNA changes and blood (MedlinePlus)	No bowel prep, no diet or medicine changes (ACS, 2026)	Every 1 to 3 years (USPSTF, 2021)	Colonoscopy
CT colonography	CT scan at an imaging center; generally sees the whole colon	Same bowel prep as colonoscopy; no sedation (ACS, 2026)	Every 5 years (USPSTF, 2021)	Colonoscopy; findings outside the colon may need more tests
Flexible sigmoidoscopy	Short scope in an office; sees the rectum and lower colon only, about a third of it	Lighter prep, usually enemas; most people are not sedated (ACS, 2026)	Every 5 years, or every 10 with a yearly FIT (USPSTF, 2021)	Colonoscopy
Colonoscopy	Scope through the whole colon; polyps can be removed during the test	Full bowel prep; sedation is usually used, so you need someone to drive you home (ACS, 2026)	Every 10 years (USPSTF, 2021)	Biopsy or removal in the same test
Blood test (such as Shield)	Blood draw; looks for DNA changes from cancer (FDA, 2024)	No special preparation (FDA, 2024)	Not on the USPSTF list (USPSTF, 2021)	Colonoscopy

Stool tests: FIT, gFOBT and stool DNA-FIT

All three are done at home and need no bowel prep. FIT and stool DNA-FIT need no changes to food or medicines; the guaiac test (gFOBT) does. (ACS, 2026) Cologuard is a stool DNA test that your provider orders and you collect at home. (MedlinePlus) The catch with every stool test is the repeat: a stool test only works as screening if you do it on schedule, and a positive result means a colonoscopy. The USPSTF says positive stool test results require a follow-up colonoscopy for the screening benefits to be achieved. (USPSTF, 2021)

Visual exams: colonoscopy, CT colonography, sigmoidoscopy

Colonoscopy and CT colonography can generally see the whole colon; flexible sigmoidoscopy sees only the lower part. (USPSTF, 2021) Colonoscopy is the only one where polyps can be removed during the same test; it needs a full bowel prep and usually sedation, and it has a small risk of bleeding, bowel tears or infection. CT colonography needs the same prep but no sedation, and anything found still needs a colonoscopy. (ACS, 2026)

Blood tests: approved, but not preferred

The FDA approved the Shield blood test on July 26, 2024, for adults 45 and older at average risk. In the study behind the approval, it detected colorectal cancer 83% of the time, and about 1 in 10 people without advanced precancerous growths got a false positive. The FDA says it does not replace a colonoscopy, and a positive result should be followed by one. (FDA, 2024)

The 2021 USPSTF recommendation does not include blood (serum) tests, citing limited evidence. (USPSTF, 2021)
The American Cancer Society says blood-based tests are not preferred at this time, and to use one only if you are not willing to have a stool test or a visual exam. It says they are not as good as the other tests at finding precancerous growths. (ACS, 2026) (ACS, 2026)
Medicare covers a blood-based test once every 3 years for people 45 to 85 at average risk without symptoms. (Medicare.gov)

What it costs

Private insurance

The Affordable Care Act requires most private plans to cover USPSTF grade A and B services without cost sharing. (42 U.S.C. 300gg-13) For colorectal screening, federal guidance adds: (ACA FAQs Part 51, 2022)

a follow-up colonoscopy after a positive stool test, CT colonography or sigmoidoscopy must be covered without cost sharing, for plan years beginning on or after May 31, 2022;
for a screening colonoscopy, items that are an integral part of it are covered too: a required specialist visit beforehand, bowel prep medicine, anesthesia, polyp removal, and the lab exam of a removed polyp.

The American Cancer Society notes that some insurers have treated the follow-up colonoscopy as diagnostic and charged a deductible or copay, and that an out-of-network doctor can cost more. It suggests asking your insurer before the test what it covers, including a colonoscopy if the result is positive. (ACS, 2026) Blood tests are not on the USPSTF list, so ask your plan before choosing one. More: preventive screenings covered by insurance.

Medicare

Medicare Part B covers each test with no cost to you if your provider accepts assignment, for people at average risk:

Medicare Part B coverage of colorectal screening tests for people at average risk
Test	Ages	How often Medicare pays
Stool blood test (FIT or gFOBT)	45 and older	Once every 12 months (Medicare.gov)
Stool DNA test	45 to 85	Every 3 years (Medicare.gov)
Blood-based test	45 to 85	Once every 3 years (Medicare.gov)
CT colonography	45 and older	Once every 60 months, or 48 months after a previous flexible sigmoidoscopy or colonoscopy (Medicare.gov)
Flexible sigmoidoscopy	45 and older	48 months after a previous flexible sigmoidoscopy or CT colonography, or 120 months after a screening colonoscopy (Medicare.gov)
Colonoscopy	No minimum age	Once every 120 months, or 48 months after a flexible sigmoidoscopy; every 24 months at high risk (Medicare.gov)

A follow-up colonoscopy after a positive Medicare-covered stool or blood test is also covered as screening, at no cost. If a polyp is removed during a colonoscopy, you pay 15% of the Medicare-approved amount for the doctor's services. (Medicare.gov)

Choosing

Questions that help narrow it down: Would I rather do a home test every year or a procedure every 10 years? Can I take a day for bowel prep and sedation, with someone to drive me? If the home test is positive, will I go on to the colonoscopy? Is the follow-up colonoscopy covered under my plan? Your doctor can help you weigh these, and anyone with symptoms, a family history or a past polyp needs a plan made with their doctor rather than this list. (USPSTF, 2021) (ACS, 2026) See also family history and screening.

Questions people ask

Is a FIT test as good as a colonoscopy?

Both are on the USPSTF list of recommended strategies for adults 45 to 75; the USPSTF does not rank one first. They differ in how often you repeat them (FIT every year, colonoscopy every 10 years), in prep and sedation, and in what happens next: a positive FIT needs a colonoscopy, while a colonoscopy can remove polyps during the same test. (USPSTF, 2021) (ACS, 2026)

Is Cologuard the same as a FIT test?

No. Cologuard is a stool DNA test, which the USPSTF calls stool DNA-FIT: it looks for DNA changes as well as blood, uses a whole bowel movement collected at home, and repeats every 1 to 3 years. A FIT looks for blood only and repeats every year. (MedlinePlus) (USPSTF, 2021) (ACS, 2026)

Is a follow-up colonoscopy free after a positive stool test?

Under federal guidance, most private plans must cover a colonoscopy after a positive stool-based test, CT colonography or sigmoidoscopy without cost sharing, for plan years beginning on or after May 31, 2022, for people the USPSTF recommendation covers. Medicare also covers it at no cost when your provider accepts assignment. The American Cancer Society still advises checking with your insurer first. (ACA FAQs Part 51, 2022) (Medicare.gov) (ACS, 2026)

Can a blood test replace a colonoscopy?

Not as a first choice. The FDA approved the Shield blood test in 2024 for adults 45 and older at average risk, and Medicare covers a blood-based test every 3 years at 45 to 85. But the USPSTF list does not include blood tests, and the American Cancer Society says they are not preferred and should be used only if you are not willing to have a stool test or a visual exam. (FDA, 2024) (Medicare.gov) (USPSTF, 2021) (ACS, 2026)

Which test needs no bowel prep?

The stool tests (FIT, high-sensitivity gFOBT and stool DNA-FIT) and blood tests need no bowel prep. CT colonography needs the same prep as a colonoscopy; sigmoidoscopy needs a lighter one, usually enemas. (ACS, 2026) (FDA, 2024)