Medicare Supplement Plan M: Coverage, Costs, Pros and Cons

Medicare Supplement Plan M is one of the standardized Medigap plans regulated by the Centers for Medicare and Medicaid Services (CMS). All insurers offering Plan M must provide identical core benefits. Plan M is a cost-sharing structure where you pay 50% of the Part A deductible in exchange for a lower monthly premium.

Medicare Supplement Plan M costs an average of $165 per month at age 65 and $230 per month at age 75, based on MoneyGeek's analysis of rates across 45 states and Washington, D.C. Where you live has more impact on your Medigap premiums than almost any other factor. South Carolina has the lowest rates at $102 per month for a 65-year-old, while New York reaches $432, more than four times as much. In community-rated states like New York, Connecticut, Arkansas, Idaho, Washington and Maine, premiums don't increase with age, so a 75-year-old pays the same as a 65-year-old.

Medicare Supplement Plan M works best for people in good health with low expected hospitalization frequency. If the annual premium savings between Plan M and Plan G exceed $868, hospitalization once per year still comes out ahead financially. Multiple hospitalizations in separate benefit periods within a single year would each trigger the 50% deductible share, increasing your total out-of-pocket exposure proportionally. Plan M also suits those who want predictable monthly costs without paying for full Part A deductible coverage they may never use.

Plan M is a poor fit for people with chronic conditions requiring frequent hospitalizations, or those who see providers that don't accept Medicare assignment. In these cases, Medicare Supplement Plan G's full Part A deductible coverage and excess charge protection justify the higher premium.

Medicare Supplement Plan G covers 100% of the Part A deductible and Part B excess charges. Plan G suits people who anticipate hospitalization or who see non-participating providers. Plan M makes financial sense when the premium gap between the two plans exceeds the cost of splitting the Part A deductible.

Both Plan M and Plan N split cost exposure with the enrollee, but in different ways. Plan N covers the Part A deductible in full while requiring copays of up to $20 for office visits and up to $50 for emergency room visits. Plan M splits the Part A deductible but carries no copays. If you have frequent outpatient visits but rare hospitalizations, Plan N's copay structure may ultimately cost more than Plan M's deductible share.

Medicare Supplement Plan F covers the Part B deductible and Part B excess charges, which Plan M doesn't include. Plan F is only available to people who became eligible for Medicare before Jan. 1, 2020. For new enrollees comparing coverage breadth, Plan G is the closest available equivalent to Plan F.