Supplemental insurance is optional, but whether you need it depends on your health costs and how much out-of-pocket risk you can handle

Medicare covers a lot, but not everything. After you meet your deductible, you still pay 20% of the cost for doctor visits and hospital care. You pay the full cost of prescription drugs until you hit a spending threshold. Supplemental insurance — also called Medigap — fills some of those gaps by paying costs Medicare leaves behind. You do not have to buy it. Some people stay on Original Medicare alone and manage the costs. Others buy Medigap to know their maximum yearly expenses upfront. The right choice depends on your health, your income, and how much unpredictability you can afford.

The decision comes down to math and peace of mind. If you have chronic conditions or see doctors regularly, Medigap gives you a predictable monthly cost instead of surprise bills. If you are healthy and rarely need care, you might save money by skipping Medigap and paying the 20% coinsurance when it comes. There is no single right answer — it depends on your situation.

Key Takeaways

  • Supplemental insurance pays some or all of the 20% coinsurance you owe after Medicare pays its share, plus some deductibles and copays.
  • You can only buy Medigap during your initial enrollment period (the six months after you turn 65 and enroll in Medicare Part B) without facing higher premiums for pre-existing conditions.
  • Medigap plans are standardized by the federal government, so Plan G from one insurer covers the same things as Plan G from another — the difference is price.
  • If you choose Medicare Advantage instead of Original Medicare, you cannot buy Medigap; you get your supplemental coverage through the Advantage plan's network and out-of-pocket limits.
  • Costs vary widely by state, age, and insurer, so comparing quotes from multiple companies is necessary to find the lowest premium for the plan you want.

What supplemental insurance actually covers

Medigap policies are labeled A through N, and each plan covers a different combination of costs. The most popular plans are G and N. Plan G pays your Part B deductible (the first $240 you owe for doctor and outpatient care in 2024), your 20% coinsurance after Medicare pays, and some other copays. Plan N is cheaper but leaves you paying a small copay at the doctor's office and a higher copay at urgent care. Plan F covers nearly everything, but it is only open to people who turned 65 before 2020.

None of the Medigap plans cover prescription drugs. If you want drug coverage, you buy that separately through a Part D plan. Medigap also does not cover dental, vision, hearing aids, or long-term care — those require separate policies or programs. The federal government sets what each plan covers, so the benefit package is identical across all insurers. A Plan G from Aetna covers exactly what a Plan G from United Healthcare covers. The only difference is the monthly premium, which varies by company, your age, your location, and the rating method the insurer uses.

When you can buy Medigap and what it costs

You have a six-month window to buy Medigap without medical underwriting — meaning the insurer cannot turn you down or charge you more because of a pre-existing condition. This window opens the month you turn 65 and enroll in Medicare Part B. If you miss this window, insurers can deny you or charge you significantly more, depending on your state's rules.

Monthly premiums range from roughly $100 to $300 or more, depending on the plan, your age, where you live, and the company. Younger enrollees pay less. Some states allow insurers to raise your premium as you age; others cap increases. A few states use "community rating," meaning everyone pays the same price regardless of age. You need to get quotes from multiple insurers in your state to see what you will actually pay.

Some employers offer retiree health coverage that works alongside Medicare. If you have that, you may not need Medigap. Check your retiree benefits booklet or call your former employer's benefits line to see what it covers and whether Medigap would duplicate coverage.

Medigap versus Medicare Advantage: which path includes supplemental coverage

You cannot have both Original Medicare with Medigap and Medicare Advantage at the same time. You have to choose one route. Original Medicare + Medigap means you go to any doctor or hospital that accepts Medicare, and Medigap covers most of your remaining costs. Medicare Advantage is an all-in-one plan run by a private insurer that includes hospital, doctor, and usually drug coverage, plus supplemental benefits like dental or vision. The trade-off is that Advantage plans have networks, prior authorization requirements, and annual out-of-pocket limits (capped at $8,300 in 2024, though that varies by plan).

If you choose Medicare Advantage, you do not buy Medigap. Your supplemental coverage comes built into the Advantage plan. If you later switch back to Original Medicare, you can buy Medigap, but you may face higher premiums or denial if you are outside your initial enrollment window and have developed new health conditions. The choice between these two paths shapes what supplemental protection you get and how much control you have over your doctors and hospitals.

How to decide whether you need supplemental insurance

Ask yourself three questions. First: do you have predictable health costs? If you see the same doctors regularly, take the same medications, and rarely need hospital care, you can estimate your yearly out-of-pocket costs and decide whether you can absorb them. If your health is unpredictable or you have a chronic condition requiring frequent care, Medigap gives you a ceiling on what you will owe.

Second: can you afford the premium? Medigap costs money every month, even in months you do not see a doctor. If your income is tight, the premium might outweigh the benefit. Some people do the math and find that paying the 20% coinsurance as it comes is cheaper than paying a monthly Medigap premium. Third: do you travel or move frequently? Original Medicare works anywhere in the United States and many countries. Medicare Advantage networks are regional. If you split time between states or travel abroad, Original Medicare with Medigap gives you more flexibility.

Steps to take if you decide to buy Medigap

First, make sure you are enrolled in Medicare Part B. Medigap requires it. You cannot buy Medigap on its own. Second, decide which plan letter (A, B, D, G, K, L, M, or N) fits your needs and budget. Plan G is the most common choice for new enrollees. Websites like Medicare.gov have a comparison tool that shows what each plan covers side by side.

Third, get quotes from at least three insurers in your state. Premiums vary widely, and the lowest-cost Plan G might save you $50 or more per month compared to the highest-cost option. Use the "Find Care Providers" tool on Medicare.gov or call insurers directly. You will need your Medicare number and your date of birth. Fourth, enroll during your initial enrollment window if possible. If you are past that window, some states allow you to buy Medigap year-round, but you may face higher premiums or medical underwriting. Check your state's rules on the National Association of Insurance Commissioners website or call your state's health insurance counseling program (usually free and run by your state's aging agency).

What happens if you do not buy Medigap

You stay on Original Medicare alone and pay the costs as they come: your Part B deductible, 20% coinsurance, and any copays. In a year with major health events — a hospital stay, surgery, or many specialist visits — these costs can add up quickly. In a healthy year with few doctor visits, you might pay very little.

You can still buy Medigap later, but if you are outside your initial enrollment window, insurers can charge you more or deny you based on your health history. Some states have "may provide issue" windows that let you buy Medigap without underwriting in certain situations — for example, if you lose employer coverage or move out of your Medicare Advantage plan's service area. Check your state's rules before you decide to wait.

Frequently Asked Questions

Can I switch Medigap plans if I change my mind?

Yes. You can switch to a different Medigap plan at any time, though you may face medical underwriting if you are outside your initial enrollment window. Some states allow switching without underwriting during an annual open enrollment period. Call your current insurer and ask about your state's rules.

Does Medigap cover prescription drugs?

No. Medigap covers cost-sharing (deductibles, copays, coinsurance) for doctor and hospital care. Prescription drug coverage comes from a separate Part D plan. You choose a Part D plan during your initial enrollment or during the annual open enrollment period in October.

What if I have both Medicare and employer health insurance?

Employer coverage is primary, and Medicare is secondary. You typically do not need Medigap because your employer plan covers most of what Medicare does not. Check your employer benefits guide or call your benefits administrator to confirm. If you retire and lose employer coverage, you have a special enrollment window to buy Medigap without penalty.

How much will Medigap cost me in the future?

Premiums increase over time due to age and inflation. Some insurers use "attained age" rating, meaning your premium rises as you get older. Others use "issue age" rating, meaning your premium is locked to the age you enrolled and rises only for inflation. Ask insurers which method they use before you enroll.

What if I cannot afford Medigap?

Some states offer low-income Medigap plans with reduced premiums. Contact your state health insurance counseling program (free, run by your state's aging agency) to learn what is available where you live. You can also explore Medicare Advantage plans, which have annual out-of-pocket limits and may include extra benefits like dental or vision.