Medicare Supplement plans are standardized insurance policies that pay for costs Medicare Part A and Part B do not cover

When you turn 65 and enroll in Original Medicare (Part A and Part B), you become responsible for deductibles, copayments, and coinsurance. A Medigap policy — the official name for Medicare Supplement insurance — is sold by private insurers and covers some or all of those out-of-pocket costs. The plans themselves are standardized by federal law, which means Plan G from one insurer covers the same benefits as Plan G from another. The difference is price and customer service, not what the policy pays for.

The "best" plan for you depends on how much you want to spend on premiums each month, how much you are willing to pay out of pocket when you see a doctor, and whether you travel outside the United States. There is no single best plan for everyone.

Key Takeaways

  • Medicare Supplement plans are standardized by the federal government, so Plan G from one company covers the same benefits as Plan G from another — only the monthly premium and company differ.
  • Plan G and Plan N are the most common choices for new retirees because they cover most costs Medicare does not, though they have different out-of-pocket limits.
  • You have a six-month window starting the month you turn 65 and enroll in Medicare Part B to buy a Medigap policy without being denied or charged more for pre-existing conditions.
  • Comparing quotes from at least three insurers for the same plan can save you hundreds of dollars per year, because premiums vary widely even though benefits do not.
  • If you miss the open enrollment window, you may still be able to buy a policy, but the insurer can charge you more or deny you coverage based on your health history.

The ten standardized plans and what they cover

The federal government defines ten Medigap plans, labeled A through N. Each plan covers a different combination of costs. Plans A, B, C, and F are older designs that are no longer sold to people newly enrolled in Medicare, though people who bought them before 2020 can keep them. If you are new to Medicare, you will choose from Plans D, G, K, L, M, or N.

Plan G is the most popular choice for new retirees. It covers the Part B deductible (which is $240 in 2024, though this amount changes yearly), all copayments and coinsurance for hospital and doctor visits, and emergency care outside the United States. You pay a monthly premium and then nothing else at the doctor's office. The only cost you are responsible for is the Part B deductible in the year you first enroll.

Plan N is less expensive than Plan G but requires you to pay a copayment at the doctor's office (usually $20) and a copayment for emergency room visits (usually $50, waived if you are admitted to the hospital). It does not cover the Part B deductible, so you pay that yourself. For people who see their doctor infrequently, Plan N can cost less overall because the lower monthly premium outweighs the copayments.

Plans D, K, L, and M cover fewer costs and have higher out-of-pocket limits. Plan K, for example, requires you to pay 50 percent of most costs until you reach an annual out-of-pocket limit (which varies by year). These plans are rarely chosen by people with stable incomes because the potential out-of-pocket costs are high, but they can make sense for someone on a very tight budget who rarely visits a doctor.

How to compare plans by cost and coverage

Start by deciding how much you want to spend on a monthly premium. If you want the lowest possible out-of-pocket costs when you see a doctor, Plan G is the clearest choice — you pay the premium and nothing else at the appointment. If you are comfortable with small copayments and want to lower your monthly bill, Plan N is worth comparing.

Once you have narrowed to one or two plans, get quotes from at least three insurers. You can request quotes directly from insurers' websites or by phone, or you can use Medicare's official plan comparison tool at Medicare.gov. Enter your zip code, the plan letter you want to compare, and the tool will show you every insurer selling that plan in your area, along with their monthly premium. Premiums for the same plan can differ by $50 to $100 per month between insurers, so comparing is worth the time.

When you compare, look at the monthly premium, any annual deductible the plan has (Plan G has none; Plan N has none), and the out-of-pocket limits for the year. Some insurers also offer discounts if you pay your premium by automatic bank transfer or if you insure multiple family members with them. Ask about these discounts when you call.

When you can buy a Medigap policy without medical underwriting

You have the strongest legal protection to buy a Medigap policy during a six-month window called the Medigap Open Enrollment Period. This window starts the month you turn 65 and enroll in Medicare Part B. During these six months, any insurer must sell you any Medigap plan at the standard rate — they cannot deny you, charge you more, or exclude pre-existing conditions.

If you miss this window, you can still buy a policy, but the insurer can require medical underwriting. This means they will ask about your health history and can charge you more or refuse to sell you a policy altogether. Some states have additional protections that allow you to buy a policy after the window closes, but these vary. If you miss the window, contact your state insurance commissioner's office to learn what options remain in your state.

The six-month window is one of the most important dates in retirement. Mark it on your calendar and buy your policy before the window closes, even if you are still deciding between plans. You can always switch to a different plan later during the annual open enrollment period (October 15 to December 7 each year), though you may face medical underwriting if you switch to a plan you did not own during your initial six-month window.

How premiums are set and why they vary between insurers

Medigap insurers use three methods to set premiums: community-rated, issue-age-rated, and attained-age-rated. Community-rated plans charge the same premium to everyone in your zip code, regardless of age. Issue-age-rated plans charge based on your age when you buy the policy — a 65-year-old pays less than a 75-year-old, but your rate does not increase as you age. Attained-age-rated plans increase your premium every year as you get older.

Attained-age-rated plans have the lowest starting premium but the highest long-term cost, because your premium rises every year. Community-rated plans are often the best value for people who plan to keep the same policy for many years, because your premium does not increase with age. Ask the insurer which method they use before you buy.

Insurers also vary in how aggressively they price their plans. Some companies are willing to sell Medigap policies at a loss to attract new customers, knowing they will make money back over time. Others price more conservatively. This is why the same Plan G can cost $120 per month from one insurer and $180 from another. Shopping around is not optional — it is the only way to find the best price.

Special situations: switching plans, moving states, and losing coverage

If you already own a Medigap policy and want to switch to a different plan, you can do so during the annual open enrollment period (October 15 to December 7). If you switch during this window, the new insurer cannot deny you or charge you more based on health. If you switch outside this window, the new insurer can require medical underwriting.

If you move to a different state, your current policy may not be available in your new state. Contact your current insurer to ask whether they sell policies in your new state. If they do not, you will need to buy a new policy from an insurer in that state. Depending on when you move, you may be able to buy without medical underwriting — contact your new state's insurance commissioner's office to learn the rules.

If you lose your Medigap coverage involuntarily — for example, because the insurer stops selling policies in your state — you have a may provide right to buy a new policy without medical underwriting, even outside the normal enrollment windows. You must buy the new policy within 63 days of losing coverage. Keep documentation of when your old policy ended.

Questions to ask your insurer before you buy

Before you enroll in a Medigap policy, ask the insurer these questions: Does the premium increase every year, and if so, by how much on average? Can I pay my premium by automatic bank transfer, and if so, is there a discount? What is the process for filing a claim, and can I file online? Does the company have a local office or phone support in my state? What happens to my policy if the company stops selling Medigap policies in my state?

Also ask whether the insurer offers any discounts for bundling (buying multiple policies) or for paying annually instead of monthly. Some companies offer small discounts for these choices, and they add up over time.

Frequently Asked Questions

Is Plan G always better than Plan N?

No. Plan G has lower out-of-pocket costs but a higher monthly premium. Plan N has a lower premium but requires copayments at the doctor's office. If you see your doctor once or twice a year, Plan N will likely cost less overall. If you see your doctor monthly, Plan G will likely cost less. Calculate both scenarios using your own doctor visit patterns to decide.

Can I buy a Medigap policy if I already have a pre-existing condition?

Yes, if you buy during your six-month Medigap Open Enrollment Period starting when you turn 65 and enroll in Part B. The insurer cannot deny you or charge you more. If you buy outside this window, the insurer can deny you or charge more based on your health history, depending on your state's rules.

What happens to my Medigap policy when I turn 75 or 85?

Your policy continues as long as you pay the premium. There is no age limit for Medigap coverage. Your premium may increase each year depending on how the insurer sets rates, but you cannot be denied renewal based on age or health.

Do I need a Medigap policy if I have a Medicare Advantage plan?

No. Medicare Advantage (Part C) is an alternative to Original Medicare and includes coverage for costs that Original Medicare does not cover. You cannot have both a Medicare Advantage plan and a Medigap policy at the same time. If you have Medicare Advantage, you do not need Medigap.

Can I switch Medigap plans if I change my mind?

Yes, during the annual open enrollment period (October 15 to December 7) you can switch to a different plan without medical underwriting. Outside this window, the new insurer can require medical underwriting. If you switch to a plan you did not own during your initial six-month enrollment window, you may face underwriting even during annual open enrollment, depending on your state.