A colonoscopy is one of the most effective screenings in preventive medicine — it can catch colorectal cancer early and often prevent it entirely by removing growths before they turn into anything serious. If you are on Medicare or about to be, the practical question is usually the same: will Medicare pay for it, and could I get a surprise bill afterward?

The short answer is that Medicare covers a screening colonoscopy at no cost to you when the provider accepts assignment — no coinsurance and no Part B deductible. But there is one important wrinkle that catches people off guard, and it is worth understanding before your procedure rather than after. This guide walks through what is covered, how often, what can trigger a cost, and how your California coverage choices fit in. It is educational information only, not medical or financial advice.

What Medicare covers for a screening colonoscopy

Medicare treats a screening colonoscopy as preventive care under Part B. When the colonoscopy is done as a routine screening — meaning you have no symptoms and the goal is early detection — Medicare pays the full approved cost and you owe nothing, as long as your doctor and the facility accept assignment (they accept Medicare’s approved amount as full payment).

That is different from most Part B services, where you normally pay a 20% coinsurance after meeting the deductible. For a true screening colonoscopy, the deductible does not apply and there is no coinsurance.

There is also no minimum age for a screening colonoscopy under Medicare. Some other screenings have age rules, but this one is based on your risk and your doctor’s recommendation.

How often Medicare pays for it

How frequently Medicare covers a screening colonoscopy depends on your risk level:

If you had a different colorectal screening test recently, timing rules can shift. For example, after a flexible sigmoidoscopy, Medicare generally covers a screening colonoscopy after 48 months.

The one thing that can create a bill: polyp removal

Here is the wrinkle. If your doctor finds and removes a polyp or takes a tissue sample during your screening colonoscopy, the procedure is reclassified from preventive to diagnostic. At that point a coinsurance can apply, even though you went in for a routine screening.

The good news is that this cost is being phased out. Federal rules are gradually lowering the coinsurance for polyp removal during a screening colonoscopy, stepping it down over the next several years until it reaches $0 by 2030. Because the exact percentage changes as the phase-down continues, check the current figure on Medicare.gov or ask your provider what you might owe if a polyp is removed. The key point is simply this: a screening that turns into a polyp removal may still carry a small cost today, and that cost is shrinking each year.

It is a fair question to ask your doctor’s office ahead of time so there are no surprises — specifically, what you would owe if a polyp is found and removed during the screening.

Stool-based tests and the follow-up colonoscopy

A colonoscopy is not the only colorectal screening Medicare covers. Depending on your situation, Medicare also covers:

If one of these at-home tests comes back positive, the follow-up colonoscopy to investigate the result is now covered as a preventive service — so that follow-up should not carry the diagnostic cost-sharing that used to apply. This is a meaningful change, because it removes a financial reason people sometimes delayed the follow-up they needed.

How your California coverage choices fit in

Coverage for the screening itself is the same nationwide — there is no separate California rule for what Medicare covers. What can differ is how the cost-sharing on a diagnostic conversion is handled, and that comes down to how you get your Medicare:

These everyday differences are exactly the kind of thing worth understanding before a procedure. Our overview of how Medicare costs work explains deductibles and coinsurance across Parts A, B, and D, and our comparison of Medicare Advantage and Medicare Supplement walks through how each path handles costs like these. The same preventive-versus-diagnostic distinction shows up elsewhere too — see how it plays out with cataract surgery, or browse every guide in our “Does Medicare cover it?” series.

When to review your coverage

You can compare and change plans during the Annual Enrollment Period (October 15 – December 7) each year, and Medicare Advantage enrollees have the Medicare Advantage Open Enrollment Period (January 1 – March 31) for one change. If you are new to Medicare, your Initial Enrollment Period is the seven-month window around your 65th birthday — the three months before your birthday month, your birthday month, and the three months after. Our Turning 65 in Southern California guide covers those timelines in detail.

If you want a second set of eyes on how a screening or a possible diagnostic procedure would be handled under your specific plan, that is the kind of question an independent broker can walk through with you at no cost. You can also compare your plan options any time.

Frequently asked questions

Does Medicare cover a colonoscopy?
Yes. Medicare covers a screening colonoscopy under Part B with no coinsurance and no Part B deductible when your provider accepts assignment. A cost can apply only if the screening becomes diagnostic — for example, if a polyp is removed.
How often will Medicare pay for a screening colonoscopy?
Once every 10 years (120 months) if you are at average risk, and once every 2 years (24 months) if you are at high risk. After a flexible sigmoidoscopy, a screening colonoscopy is generally covered after 48 months.
Is there a minimum age for a Medicare screening colonoscopy?
No. Unlike some screenings, there is no minimum age requirement for a screening colonoscopy under Medicare; coverage is based on your risk and your doctor’s recommendation.
Why did I get a bill after a “free” screening colonoscopy?
Usually because a polyp was found and removed, which reclassifies the visit from preventive to diagnostic. That triggers a coinsurance, which federal rules are phasing down toward $0 by 2030. Ask your provider what you might owe if a polyp is removed.
Does Medicare cover the colonoscopy if my at-home stool test was positive?
Yes. A follow-up colonoscopy after a positive Medicare-covered stool test (such as a FIT or a multi-target stool DNA test) is now covered as a preventive service.
Do I pay less with a Medigap plan or a Medicare Advantage plan?
It depends. A Medigap policy may cover some or all of any coinsurance from a diagnostic conversion, while a Medicare Advantage plan sets its own copays and network rules. Comparing how each path handles these costs before you need care is the best way to avoid surprises.

Sources & official references

This is a non-government resource and is not affiliated with or endorsed by Medicare.gov or the federal Medicare program. An independent broker may not offer every plan available in your area. For all of your options, contact Medicare.gov, 1-800-MEDICARE, or your local State Health Insurance Assistance Program (SHIP) — in California, the Health Insurance Counseling and Advocacy Program (HICAP). Last reviewed: August 2026. Sources: Medicare.gov (colonoscopy and colorectal cancer screening coverage under Part B). The polyp-removal coinsurance is being phased down to $0 by 2030; confirm the current percentage with Medicare.gov or your provider. Educational information only, not medical, financial, or individualized advice.