Medicare Supplement Plan K: Coverage, Costs, Pros & Cons

Medicare Supplement Plan K is a standardized Medigap policy that covers 50% of most Original Medicare cost sharing after Medicare pays its portion. CMS sets the benefits for all Plan K policies sold in the U.S., so coverage is identical regardless of which insurer sells it. Premiums vary by insurer, state and pricing method. 

Plan K is designed for Medicare enrollees who want a lower monthly premium and can absorb more out-of-pocket costs during the year. Its 2026 annual out-of-pocket limit of $8,000 caps total exposure once covered Part A and Part B co-insurance and copayments accumulate, per CMS. Once you reach that limit, Plan K pays 100% of covered costs for the rest of the calendar year.

Medicare Supplement Plan K pays 100% of Part A hospital co-insurance and 50% of most other Medicare cost sharing once Original Medicare has paid its share. The 2026 out-of-pocket limit of $8,000 applies to covered Part A and Part B co-insurance and copayments, per CMS. After you reach that limit, Plan K pays 100% of covered costs for the rest of the calendar year.

Medicare Supplement Plan K excludes three cost categories that other Medigap plans often cover. These gaps are the main tradeoff for Plan K's lower monthly premium. See what Medicare doesn't cover for a broader breakdown of Original Medicare exclusions. 

• Part B deductible: You pay the full 2026 Part B deductible of $283 before Plan K benefits apply to Part B costs, per CMS.
• Part B excess charges: Plan K doesn't cover the excess when a provider doesn't accept Medicare assignment and bills up to 15% above the Medicare-approved amount.
• Foreign travel emergency: Plan K provides no coverage for emergency care outside the U.S.

Medicare Supplement Plan K has a lower monthly premium than most Medigap plans because it covers 50% of most Medicare cost sharing rather than 100%. That tradeoff works well for healthy retirees who use Medicare services infrequently but want a cap on worst-case annual costs. The 2026 out-of-pocket limit of $8,000 provides that financial floor. Policyholders who use Medicare often may pay more out of pocket than they would under a Plan G or Plan N policy.

Medicare Supplement Plan K premiums start at $95 per month for a 65-year-old on issue age pricing. Costs rise with age, pricing method and state of residence. A 75-year-old pays $137 to $140 per month depending on the pricing structure their insurer uses. Annual costs range from $1,141 to $1,677 across the age and pricing combinations in the table below. 

For a broader look at how Medigap premiums compare across all standardized plans, see Medicare Supplement plan costs.

Medicare Supplement Plan K covers 50% of most Medicare cost sharing and has the highest out-of-pocket limit of the plans compared here. Plan L covers 75% and caps annual exposure at $4,000. Plan G and Plan N cover 100% of most cost sharing but have no annual out-of-pocket limit. Plan F covers nearly everything but isn't available to Medicare enrollees first eligible on or after January 1, 2020.

*Plan N pays 100% of Part B co-insurance but requires copays up to $20 for some office visits and up to $50 for emergency room visits that don't result in inpatient admission.

Medicare Supplement Plan K works best for Medicare enrollees who want lower monthly premiums and rarely use specialist or hospital services. But the 50% cost-sharing structure means unpredictable annual costs during active health years. The 2026 out-of-pocket limit of $8,000 provides the financial floor on that exposure. Policyholders who use Medicare services regularly may pay less overall with Plan G or Plan N, despite those plans' higher premiums.

Enrolling in Medicare Supplement Plan K requires active Medicare Part A and Part B coverage. The best time to buy is during your 6-month Medigap Open Enrollment Period, which starts the first day of the month you turn 65 and are enrolled in Part B, per Medicare.gov. Buying during this window means insurers can't deny you coverage or charge higher premiums based on health history. Not yet enrolled? See how to sign up for Medicare first.

Medicare Supplement Plan K is a lower-premium Medigap option that covers 50% of most Medicare cost sharing. Premiums start at $95 per month for 65-year-olds on issue age pricing. The 2026 out-of-pocket limit of $8,000 caps worst-case annual exposure, per CMS. Plan K works best for healthy enrollees who want lower monthly premiums and use Medicare services infrequently. But policyholders who use Medicare often pay less overall with Plan G or Plan N.

We've answered the most frequently asked questions about Medicare Supplement Plan K: