Original Medicare pays for much of your care, but not all of it. You still face deductibles, a 20% share of most doctor and outpatient bills and daily charges for long hospital or nursing facility stays. A Medicare Supplement Insurance policy, called Medigap, helps pay those costs.
How Medigap works
Medigap policies are sold by private insurance companies. You must have Medicare Part A and Part B, and you pay a monthly premium to the insurer, on top of your Part B premium. When you get care, Medicare pays its share first, then your Medigap policy pays its share of what is left.
Medigap only works with Original Medicare. You cannot use it with a Medicare Advantage plan, and it is illegal for anyone to sell you one if you are in Medicare Advantage, unless you are switching back to Original Medicare.
Standardized plans
In most states, Medigap plans are standardized and named with letters: A, B, C, D, F, G, K, L, M and N. Every plan with the same letter has the same basic benefits, no matter which company sells it. Massachusetts, Minnesota and Wisconsin standardize their plans differently.
A few popular choices:
- Plan G covers almost all gaps in Original Medicare except the Part B deductible ($283 in 2026). Once you pay that deductible, you generally pay nothing more for Medicare-covered services.
- Plan N usually has a lower premium. You pay the Part B deductible, copays of up to $20 for some office visits and up to $50 for emergency room visits that do not result in an inpatient admission.
- Plans K and L have lower premiums and pay a percentage of costs, with a yearly out-of-pocket limit.
Plans C and F, which also cover the Part B deductible, are not available to people who became eligible for Medicare on or after January 1, 2020.
The best time to buy
Your Medigap open enrollment period lasts 6 months. It starts the first month you are both 65 or older and enrolled in Part B. During this time:
- Insurers must sell you any Medigap policy they offer in your state.
- They cannot charge more because of your health.
- They cannot make you wait for coverage of pre-existing conditions in most cases.
After this window closes, insurers in most states can ask health questions and charge more or decline to sell you a policy. If you delay Part B because you are still working, your Medigap window starts when you do sign up for Part B.
How insurers set prices
Since benefits are standardized, price is the main difference between companies. Insurers use one of three pricing methods:
- Community-rated: everyone pays the same regardless of age.
- Issue-age-rated: based on your age when you buy, so the price does not rise because you get older.
- Attained-age-rated: based on your current age, so the price rises as you age.
All three can still rise with inflation and claims. Ask each company how it prices policies and how much its premiums have increased in recent years.
What Medigap does not cover
- Prescription drugs. You need a separate Part D plan.
- Long-term care, routine dental, vision and hearing aids.
- Private-duty nursing.
Some plans cover emergency care during travel outside the US, up to plan limits.
How to shop
- Decide which letter plan fits your budget and needs.
- Use the Medigap tool on Medicare.gov to see which companies sell plans in your ZIP code.
- Get quotes from several companies for the same letter plan.
- Ask about pricing method, discounts and rate history.
- Talk with your SHIP counselor if you want a second opinion.
