Preventive Health · 2026-08-27 · 4 min read
Colorectal Cancer Screening Options: Colonoscopy, FIT, and Stool DNA
The screening starts at 45. Here is how the home stool tests compare to colonoscopy, and how to pick one you will actually do.
Colorectal cancer is the second leading cause of cancer death in the United States and one of the most preventable. It grows slowly from polyps that can be found and removed years before they turn into cancer. Screening works. The problem is that about a third of eligible adults are not up to date.
Part of the reason is that many people think screening means colonoscopy. It does not have to. There are home tests that most guidelines accept as a first line option. The best test is the one you will complete.
When to start
Age 45 for people at average risk, per the USPSTF and the American Cancer Society. The age dropped from 50 in 2021 because rates in younger adults have been rising.
Earlier for people with a first degree relative who had colorectal cancer or advanced polyps, with inflammatory bowel disease, or with certain inherited syndromes. Those people are also usually steered to colonoscopy rather than a stool test.
Screening runs to 75 as a routine matter, then individually to 85.
The options
| Test | Interval | Where | What it finds | Follow up if positive |
|---|---|---|---|---|
| FIT | Every year | Home | Blood in stool | Colonoscopy |
| Stool DNA with FIT | Every 1 to 3 years | Home | Blood and altered DNA in stool | Colonoscopy |
| Colonoscopy | Every 10 years | Facility, sedated | Polyps and cancer directly, and removes polyps | None, it is the follow up |
| CT colonography | Every 5 years | Facility, no sedation | Polyps and cancer on imaging | Colonoscopy |
| Flexible sigmoidoscopy | Every 5 years | Facility | Lower colon only | Colonoscopy |
FIT
The fecal immunochemical test detects human hemoglobin in stool. It replaced the older guaiac test, which required diet changes and had more false results. You collect a small sample at home with a brush or probe, seal it, and mail it or drop it at a lab. No prep. No diet restrictions.
A single FIT catches roughly three quarters of cancers and a smaller share of advanced polyps. Because it is repeated every year, the cumulative catch rate over a decade is high. It is the cheapest option and the one most health systems mail out.
A positive result is not a cancer diagnosis. Most positives are from polyps, hemorrhoids, or other benign sources. It does mean a colonoscopy, and skipping that step erases the value of the test.
Stool DNA with FIT
Sold under the brand Cologuard in the US. Combines a FIT with tests for DNA changes shed by polyps and tumors. Requires a full stool sample collected in a kit and shipped to the lab. Catches more cancers than FIT alone in a single test, and more advanced polyps, at the cost of more false positives. Approved for every three years, though some guidelines say one to three. Costs more than FIT, and insurance coverage of the follow up colonoscopy after a positive is a known sore spot. Check before you order.
Colonoscopy
The reference standard. A flexible scope examines the whole colon, and polyps are removed during the same procedure. It requires a day of bowel prep, sedation, and someone to drive you home. Done every ten years if normal, sooner if polyps are found.
It is the right choice for people at higher risk, for anyone with symptoms, and for anyone who prefers to do this once a decade rather than yearly. It carries a small risk of bleeding or perforation, higher in older adults.
How to choose
Ask three questions.
Am I at average risk? If not, colonoscopy. Do not start with a stool test.
Will I actually do a yearly test? If yes, FIT is the simplest and cheapest path. If you suspect you will let it lapse, a colonoscopy every ten years may be the more reliable plan.
What does my insurance cover? Screening tests are covered without cost sharing under most US plans. The gap is that a colonoscopy after a positive stool test is sometimes billed as diagnostic. Federal rules now require it to be covered as screening for most plans, but confirm.
Doing a home test right
- Check the expiration date on the kit.
- Do not collect during menstruation or with active hemorrhoid bleeding. Wait a few days.
- Follow the collection instructions exactly. Too much sample is as bad as too little.
- Return it within the window on the box, usually a few days for FIT and a couple of weeks for stool DNA.
- If it comes back positive, schedule the colonoscopy. That is the test doing its job.
Symptoms are a different matter. Blood in the stool, a change in bowel habit lasting weeks, unexplained weight loss, or abdominal pain that does not go away should go to a clinician regardless of age or screening history. Screening is for when you feel fine.
By the Ribbon Health Press editorial team. Reviewed against current clinical guidelines at publication. Report an error: editors@ribboncheckup.org. See our editorial policy.