Short answer: a screening colonoscopy is free — $0 — if your provider accepts assignment and no polyp is found. But your provider may find and remove a polyp, or take a tissue sample, during that same screening. Then the visit becomes a diagnostic procedure. You then owe 15% coinsurance of the Medicare-approved amount, and the Part B deductible is waived. This is the biggest source of "surprise" colonoscopy bills. The type of procedure changes mid-visit, based on what the doctor finds. It does not depend on anything you chose.
Why a "Free" Screening Isn't Always Free
Medicare covers screening colonoscopies as prevention. They look for colorectal cancer before you have symptoms. If your provider accepts assignment and finds nothing that needs treatment, you pay nothing. But screening and treatment often happen in the same visit. Say the doctor sees a polyp. The usual practice is to remove it right then, not schedule a second procedure. When that happens, Medicare's billing rules change the service from "screening" to "diagnostic." You're no longer just looking. You're treating something that was found.
What You Actually Pay
If a polyp or tissue is removed during a screening colonoscopy, you owe 15% of the Medicare-approved amount for the provider's services. The Part B deductible does not apply to this charge. If the procedure happens in a hospital outpatient department or ambulatory surgical center, you also pay the facility a 15% coinsurance.
That 15% rate isn't permanent. It's a middle step in a planned drop toward $0. Section 122 of the Consolidated Appropriations Act sets the coinsurance for a screening test that becomes diagnostic because of polyp removal. It follows this schedule:
- 2022: 20% coinsurance.
- 2023–2026: 15% coinsurance (today's rate).
- 2027–2029: 10% coinsurance.
- 2030 and after: 0% coinsurance. The screening-turned-diagnostic charge goes away entirely.
How Often Screening Colonoscopies Are Covered
How often Medicare pays for a screening colonoscopy depends on your risk level:
- Once every 24 months if you're at high risk for colorectal cancer.
- Once every 120 months if you're not high risk, or every 48 months after a previous flexible sigmoidoscopy.
Staying within those windows helps keep the procedure covered as a screening. See Understanding Your Costs for how Part B coinsurance and deductibles work in general. See Medicare Part B for what else medical insurance covers.
What to Ask Before the Procedure
You can't know in advance whether a polyp will be found. So you can't avoid this cost by planning around it. What you can do is ask your provider's office, before the visit, how they bill if a polyp is removed during a screening. Some practices can explain the billing codes in advance so the bill isn't a surprise. Do you get a bill you don't understand? Our common billing mistakes guide covers how to check a claim before you pay it.
Common Questions
Does Medicare cover colonoscopies for free?
A screening colonoscopy is free if your provider accepts assignment and no polyp is found. If a polyp is found and removed during that same screening, the visit becomes diagnostic and you owe coinsurance.
How much will I owe if a polyp is removed?
For 2023 through 2026, you owe 15% of the Medicare-approved amount, with no Part B deductible. That coinsurance is scheduled to drop to 10% for 2027 through 2029, then to 0% starting in 2030.
Does this happen with other free screenings too?
The screening-to-diagnostic switch is most visible with colonoscopies, but the same idea applies widely. A preventive visit stops being free once it turns into treatment for something found during that visit. Ask your provider whether a certain step is still part of the screening or has become diagnostic care.