Medicare 2026

Original Medicare's 20% Coinsurance Has No Yearly Cap: What Can Limit Your Costs

Original Medicare covers a lot, but it was not built with a yearly spending ceiling. After you meet the Part B deductible, you generally pay 20 percent of the Medicare-approved amount for Part B services — and that 20 percent keeps going for as long as you keep getting care. For a routine year, that may feel manageable. For a year with surgery, cancer treatment, or a long rehab stay, it can add up quickly. Understanding how that 20 percent works, and what can put a ceiling on it, is one of the most useful things you can do early in your Medicare journey.

How the 20 percent actually works

The Medicare-approved amount is the payment amount Original Medicare sets for a covered service or item. Medicare pays its share of that amount, and you pay yours. For most Part B services, once you meet the yearly Part B deductible ($283 in 2026), you typically pay 20 percent of the approved amount, as long as the provider accepts assignment.

A doctor, provider, or supplier who accepts assignment agrees to charge only the Medicare deductible and coinsurance, and usually waits for Medicare to pay its share before asking you to pay yours. That is a quiet but powerful protection: it means you cannot be surprised by a bill above the approved amount from an assignment-accepting provider. For Part B-covered drugs, doctors and pharmacies must accept assignment, so you should never be asked to pay more than the coinsurance or copayment for the drug itself.

There is no annual stop-loss built into Original Medicare. Twenty percent of a $200 office visit is modest. Twenty percent of a long hospital-based course of care — plus repeated outpatient services, imaging, and specialist visits — is a different story. And remember, the Part B premium ($202.90 a month in 2026, higher for some people with higher incomes) is owed every month even in a year when you use no Part B services.

What can put a ceiling on your costs

Original Medicare pairs well with several kinds of supplemental coverage, each of which works differently:

Medigap (Medicare Supplement Insurance). Medigap policies help pay some of the costs Original Medicare leaves to you, such as coinsurance and copayments. Most Medigap plans do not have a separate yearly out-of-pocket limit, because they cover the coinsurance directly. Two plans — K and L — work differently: they share a portion of costs with you until you hit a yearly cap. In 2026, that cap is $8,000 for Plan K and $4,000 for Plan L. CMS announced in October 2026 that the 2027 limits are $8,360 for Plan K and $4,180 for Plan L. Once you meet the limit and the yearly Part B deductible, the plan pays 100 percent of covered services for the rest of the calendar year.

Medicaid. If you qualify for Medicaid alongside Medicare, Medicaid may pick up cost-sharing. People in the Qualified Medicare Beneficiary (QMB) program cannot be billed by Medicare providers for Part A or Part B deductibles, coinsurance, or copayments (in some cases a small Medicaid copayment may apply). Your Medicare Summary Notice shows whether you are enrolled in QMB — a useful thing to check if you ever receive a bill you think you should not owe.

Employer, retiree, or union coverage. These plans vary widely, but they often help limit cost-sharing. If you have this coverage, ask the benefits administrator exactly how it coordinates with Medicare.

Medicare Advantage. A Medicare Advantage plan replaces how you get your Part A and Part B benefits and has its own yearly out-of-pocket limit, which varies by plan. In exchange, plans typically use provider networks and plan rules. Original Medicare paired with Medigap, by contrast, generally lets you see any provider in the country that accepts Medicare and gives you more predictable cost-sharing, but Medigap has its own premium. Neither approach is better for everyone; the right fit depends on your health, your budget, your providers, and how you like to make decisions.

Part D fits into the picture, too

Prescription drugs are usually covered by a stand-alone Part D plan when you have Original Medicare. Part D now has a yearly out-of-pocket cap: $2,100 in 2026, rising to $2,400 in 2027. The most any Part D plan may charge as a deductible in 2027 is $700. The Part D base beneficiary premium for 2027 is $41.33 — a national figure used in the late-enrollment penalty; actual plan premiums are set plan by plan.

Important dates and announcements

• Annual Enrollment (Open Enrollment) for 2027: October 15 – December 7, 2026; choices take effect January 1, 2027.
• COLA: The Social Security Administration announced on October 14, 2026 a 3.6 percent cost-of-living adjustment for benefits payable beginning January 2027.
• 2027 Part B premium, Part B deductible, and IRMAA income brackets: not yet announced. CMS announces these in the fall, usually November.

A note for people with Medicaid or Extra Help

Since 2025, if you have Medicaid or Extra Help, you have a monthly Special Enrollment Period to move to Original Medicare with a stand-alone Part D plan, or to switch stand-alone Part D plans. Full-benefit dual-eligible people can also join an integrated D-SNP in any month. This gives you more flexibility to adjust your coverage when something in your life or care changes.

Where to go next

For official, up-to-date information — including the 2027 Part B figures when CMS releases them — visit Medicare.gov or call 1-800-MEDICARE (1-800-633-4227), TTY 1-877-486-2048. Taking an hour to understand how your coinsurance works, and what can cap it, is time well spent before you need the care.