Medicare Supplement plans fill gaps that Original Medicare leaves open, but they don't replace Medicare

Medicare Supplement insurance (also called Medigap) pays some of the costs that Original Medicare doesn't cover — like copayments, coinsurance, and deductibles. You must have Original Medicare Part A and Part B to buy a Medigap plan. The plan works alongside Medicare; it is not a substitute for it, and you keep paying your Medicare premiums while also paying a separate Medigap premium to a private insurance company.

The key truth about Medigap is that the coverage is standardized. The federal government defines ten different Medigap plans (labeled A through N, with some variations by state), and every insurance company that sells Plan G, for example, must offer the exact same benefits. The price varies by company and by where you live, but the coverage does not. This means you can compare plans by looking at what each letter covers, not by reading different company brochures.

Medigap does not cover everything. It does not pay for long-term care, dental work, vision care, hearing aids, or prescription drugs. If you need prescription drug coverage, you enroll in a separate Part D plan. If you want dental or vision, you purchase those separately or through a Medicare Advantage plan instead.

Key Takeaways

  • Medigap plans are sold by private insurance companies but follow federal rules about what each plan letter must cover.
  • You must have Original Medicare Part A and Part B before you can buy Medigap; the two work together, not instead of each other.
  • The ten standardized plans (A through N) offer different levels of coverage, and Plan G and Plan N are the most commonly chosen by new enrollees.
  • Medigap does not cover prescription drugs, dental, vision, hearing aids, or long-term care, so you may need separate coverage for those.
  • You can switch Medigap plans or companies, but your age and health history may affect your premium or whether you are accepted.

The ten standardized Medigap plans and what they cover

Each Medigap plan is identified by a letter, and the federal government sets what benefits each letter must include. Plans A, B, D, G, K, L, M, and N are available in all states. Plans C and F are closed to people who became may be able to access for Medicare after December 31, 2019, though people already enrolled can keep them.

Plan G and Plan N cover the most common gaps for new enrollees. Plan G pays your Part B deductible, coinsurance, and copayments, plus excess charges if your doctor bills above Medicare's approved amount. Plan N is similar but requires you to pay a small copayment at the doctor's office and for emergency room visits. Plan A is the most basic and least expensive, covering only the Part B coinsurance and copayments. Plan D, K, and L offer middle-ground coverage at lower premiums than G or N.

You can view a detailed comparison chart on the Medicare.gov website showing exactly what each plan covers. Because the benefits are standardized, the only reason to choose one company's Plan G over another's is price and customer service — the coverage is identical.

How Medigap premiums are set and what affects your cost

Three pricing methods exist: community-rated (everyone in your state pays the same premium regardless of age), issue-age-rated (your premium is based on your age when you first enroll), and attained-age-rated (your premium increases as you get older). Most companies use attained-age rating, which means your premium will rise over time even if you stay with the same plan and company.

Your premium also depends on where you live. A Plan G in Florida costs more than the same plan in a rural state because healthcare costs and claims experience vary by region. Insurance companies set their own rates within state rules, so comparing quotes from multiple companies is worth the time — the difference between the cheapest and most expensive Plan G in your area can be hundreds of dollars per year.

You do not face medical underwriting (health questions) if you enroll during your Medigap open enrollment period, which runs for six months starting the month you turn 65 and enroll in Medicare Part B. Outside that window, some companies will deny you or charge more based on your health history. A few states offer may provide issue rights at other times — for example, if you lose employer coverage or move out of state — but these are limited.

Medigap versus Medicare Advantage: which path to choose

Medicare Advantage (Part C) is a different route entirely. Instead of Original Medicare plus Medigap, you enroll in a private plan that includes Part A, Part B, and usually Part D all in one. Medicare Advantage plans often have lower or zero premiums, but they come with networks, prior authorization requirements, and out-of-pocket maximums that Medigap does not impose.

Medigap gives you freedom to see any doctor or hospital that accepts Medicare, with no referrals or approval delays. You pay your Medigap premium and your Medicare premiums, then your out-of-pocket costs are limited by what the plan covers — but there is no annual out-of-pocket maximum the way Medicare Advantage has. If you have a very expensive year, Medigap can cost more.

The choice depends on your health, your doctors, and your budget. If you have a chronic condition and see specialists, Medigap's freedom to see anyone may be worth the higher premium. If you are generally healthy and want the lowest monthly cost, Medicare Advantage may make sense. You can switch between the two during the annual open enrollment period (October 15 to December 7), though switching from Medigap to Medicare Advantage is easier than the reverse.

When you can enroll in Medigap and what happens if you miss the window

Your best opportunity to enroll is during the six-month Medigap open enrollment period that begins the month you turn 65 and enroll in Medicare Part B. During this window, insurance companies cannot deny you based on health conditions, cannot charge you more because of your health, and cannot impose waiting periods. This protection is federal law.

If you enroll after this window closes, you enter what is called the may provide issue period only if you may have access to. may have access to reasons include losing employer or union retiree coverage, moving out of state, or having your Medicare Advantage plan leave your area. Each state defines its own may provide issue rules, so what qualifies in one state may not in another. Contact your state's insurance commissioner's office or call 1-800-MEDICARE to learn what applies where you live.

Outside may provide issue periods, companies can medically underwrite you — meaning they can ask about your health history, deny your process, or charge a higher premium. Some companies are more willing to do this than others, but there is no federal requirement to cover you. This is why enrolling during your initial six-month window is so important: it is the only time you have a legal right to any plan you choose at the standard rate.

How to compare Medigap plans and find current quotes

Start by deciding which plan letter fits your needs and budget. Medicare.gov has a plan comparison tool that shows what each plan covers side by side. Once you know which plan you want, get quotes from at least three insurance companies in your state. Most companies let you request a quote online or by phone without committing to anything.

The National Association of Insurance Commissioners (NAIC) website lists state-specific resources and complaint ratios for insurance companies, which can help you assess customer service. Your state's insurance commissioner's office also publishes a Medigap shopper's guide with local rates and company contact information — this is free and often the fastest way to see what is available in your area.

Do not assume the cheapest plan is the best deal. A company with a lower premium might have higher customer service complaints or might raise rates more aggressively each year. Reading recent reviews and checking the company's complaint history is worth the extra step. Once you choose a company and plan, you can enroll by phone, online, or through an agent.

What happens to your Medigap coverage if you move or change plans

If you move to a different state, your current Medigap plan may not be available in your new state, or the same company may not operate there. You have the right to switch to a different Medigap plan in your new state without medical underwriting for 63 days after you move. This is a may provide issue right, so use it if your current plan is not available.

If you want to switch Medigap plans or companies while staying in the same state, you can do so during the annual open enrollment period (October 15 to December 7) or during your birthday month. Outside these windows, you may face medical underwriting. Some states offer additional switching rights, so check with your state insurance commissioner's office if you are outside the standard periods.

When you switch plans, there is usually a gap in coverage of a few days while the new company processes your enrollment. Make sure your old plan does not end before your new plan begins. If you are switching companies but keeping the same plan letter, the new company will take over on the first of the month following your approval.

Frequently Asked Questions

Can I have both Medigap and Medicare Advantage at the same time?

No. Federal law prohibits you from enrolling in both. You must choose one path: Original Medicare with Medigap, or Medicare Advantage. If you have both, Medicare will cancel your Medigap plan. You can switch between them during open enrollment, but you cannot hold both simultaneously.

Does Medigap cover prescription drugs?

No. Medigap covers gaps in Original Medicare's medical costs, but not drugs. You must enroll in a separate Medicare Part D prescription drug plan. You can enroll in Part D at the same time you enroll in Medigap, and the two work together to cover your healthcare costs.

What if my Medigap company raises my premium too much?

You can switch to a different company or plan during the annual open enrollment period (October 15 to December 7) or during your birthday month without medical underwriting. Compare quotes from other companies before your renewal date so you know your options. Some states have rate review processes that limit how much companies can raise premiums, so check your state insurance commissioner's website.

Do I still pay Medicare premiums if I have Medigap?

Yes. You pay your Medicare Part B premium to Medicare and your Medigap premium to the private insurance company. Most people also pay a Part A premium if they did not work long enough to may have access to for premium-free Part A, though this is less common. Medigap is supplemental coverage, not a replacement for Medicare.

Can I switch from Medigap to Medicare Advantage?

Yes, during the annual open enrollment period (October 15 to December 7). Switching from Medicare Advantage back to Medigap is harder — you may face medical underwriting unless you may have access to for a may provide issue right. If you think you might want to switch back to Medigap later, ask your state insurance commissioner about your rights before you make the change.