What Medicare Supplement Standardized Plans Are
Medicare Supplement standardized plans are private insurance policies that fill gaps in Original Medicare (Part A and Part B). The federal government standardized the benefits so that every Plan G, for example, offers the same core coverage regardless of which insurance company sells it. Insurers can differ only in price, underwriting rules, and extra perks such as foreign travel emergency coverage or gym memberships. This structure lets beneficiaries compare apples to apples when choosing a Medigap policy.
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Standardization applies in most states, but Massachusetts, Minnesota, and Wisconsin use their own standardized plan designs that differ from the national model. If you live in one of those states, the letter codes mean different things, and the comparison rules below apply with adjustments.
How the Letter System Works
The standardized system uses letters A through N to identify benefit packages. Plans with the same letter must offer identical basic benefits, though insurers may offer high-deductible versions of certain plans. The letters do not rank in quality; they simply describe which benefits are included. Because the federal definition is fixed, a Plan F sold by Company X is required to match a Plan F sold by Company Y in core coverage.
Several letters have been phased out as Medicare policy changed. Plan F is no longer available to people newly eligible for Medicare on or after January 1, 2020, and Plan C was phased out at the same time for the same reason. These plans remain available to anyone who was eligible before that date and continues to enroll.
Core Benefits Across Standardized Plans
Medicare Supplement standardized plans cover some combination of the following cost-sharing items that Original Medicare does not pay:
- Part A hospital coinsurance and hospital costs for an additional 365 days after Medicare benefits are used up
- Part A skilled nursing facility coinsurance
- Part B coinsurance or copayment
- Blood transfusions (first three pints)
- Part A and Part B deductibles, depending on the plan
- Foreign travel emergency care (80% of covered costs, with a lifetime limit)
- Excess charges, or the difference between what a doctor charges and what Medicare approves, on Part B services
Comparing Popular Letter Plans
| Plan | Part A Deductible | Part B Deductible | Part B Excess Charges | High-Deductible Option |
|---|---|---|---|---|
| Plan A | Covered | Not covered | Not covered | No |
| Plan G | Covered | Covered | Covered | Yes |
| Plan N | Covered | Covered | Covered | No |
Plan G is often the most popular standardized plan for new enrollees because it provides the most comprehensive coverage short of the now-unavailable Plan F. It covers the Part B deductible, which in 2024 is $240 per year, along with all coinsurance and copayments. Plan N requires the beneficiary to pay a small copay for outpatient visits and emergency room visits, which lowers the monthly premium.
Why Standardization Matters When Shopping
Because standardized plans must match by letter, the main variable in your decision is price. Two companies can both sell a Plan G, but monthly premiums can differ by hundreds of dollars. Insurers may also offer additional benefits not required by the standard, such as coverage for the Part B deductible in the first year or dental and vision riders, but these extras vary by company and are not part of the standardized definition.
Enrollment Rules and Guaranteed Issue
The best time to buy any Medicare Supplement standardized plan is during the Medigap open enrollment period, which begins on the first day of the month you turn 65 and are enrolled in Medicare Part B. During those six months, insurers must sell you any plan they offer, regardless of health history. Outside that window, companies can medically underwrite you, which means they can deny coverage or charge higher premiums based on your health.
What to Watch for When Comparing Costs
Premiums vary widely even for identical letter plans. Pricing methods include community-rated (same premium for everyone), issue-age-rated (based on your age at purchase), and attained-age-rated (based on your current age, which goes up over time). A lower monthly premium can still mean higher total costs if the insurer raises rates frequently. Before enrolling, check the company's rate-increase history and whether the premium is guaranteed level or can change annually.