A Medicare Supplement Policy Fills Gaps That Original Medicare Leaves Behind

A Medicare Supplement policy (also called Medigap) is private insurance you buy to cover costs that Original Medicare does not pay. Original Medicare covers a lot, but it leaves you responsible for deductibles, copayments, and coinsurance. A Medigap policy picks up some or all of those out-of-pocket costs, depending on which plan you choose.

You buy Medigap from a private insurance company, not from Medicare itself. It works alongside Original Medicare (Parts A and B) — it does not replace it. You keep your Medicare card and use it the same way. The Medigap policy straightforward pays what Medicare does not.

Key Takeaways

  • Medigap policies are sold by private insurers and cover deductibles, copayments, and coinsurance that Original Medicare leaves you to pay.
  • Ten standardized Medigap plans exist (labeled A through N), and each covers a different combination of costs — the same plan letter covers the same benefits no matter which company sells it.
  • You can enroll in Medigap during your initial Medicare enrollment period or during the annual open enrollment period, though waiting may cost you more in premiums.
  • Medigap does not cover prescription drugs, long-term care, dental, vision, or hearing — you may need separate coverage for those.
  • Your age, location, and health history at the time you enroll affect your premium, and some states allow insurers to consider your health status.

The Ten Standardized Medigap Plans and What They Cover

Medicare defines ten standard Medigap plans, labeled A, B, C, D, F, G, K, L, M, and N. Each plan covers a specific set of costs. Plan F and Plan C are no longer sold to people new to Medicare as of 2020, but people who had them before that date can keep them. The letter does not indicate quality or company — it indicates which costs are covered. Plan G from Company X covers exactly the same benefits as Plan G from Company Y.

Plan A is the most basic and least expensive. It covers Medicare Part A coinsurance and copayments, Part B copayments, and the first three pints of blood. Plan G is one of the most popular because it covers most of what Plan F covered before the rule change. Plan N is less expensive than Plan G but requires you to pay small copayments at the doctor's office and emergency room.

You can compare the exact coverage of each plan side by side on Medicare.gov. The differences matter because they directly affect what you pay out of pocket when you see a doctor or go to the hospital.

How Medigap Premiums Are Calculated

Your Medigap premium depends on three main factors: the plan you choose, where you live, and your age at the time you enroll. Premiums vary by state and by insurance company. The same Plan G might cost $120 per month with one company and $180 with another in the same state.

Age matters significantly. If you enroll in Medigap during your initial Medicare enrollment period (which begins three months before the month you turn 65), you typically pay lower premiums than if you wait. Some states allow insurers to charge more if you enroll later, a practice called underwriting. Other states do not allow this. Waiting to enroll can mean paying higher premiums for the rest of your life, so timing your enrollment matters.

Premiums also increase as you age. Most Medigap policies increase your premium each year, though the amount varies by company and plan. Some companies use age-attained pricing (your premium rises as you get older), while others use issue-age pricing (your premium is based on your age when you first enroll and does not rise as you age, though it still increases annually for other reasons).

When You Can Enroll in Medigap and Why Timing Matters

Your best opportunity to enroll in Medigap without medical underwriting is during your Medigap open enrollment period. This period lasts six months and begins the first day of the month you turn 65 and are enrolled in Medicare Part B. During these six months, you can buy any Medigap plan at the best rates, regardless of your health history.

If you miss this window, you can still buy Medigap, but the rules change. Some states allow insurers to deny you coverage or charge more based on your health conditions — a process called medical underwriting. Other states have protections that limit or prevent this. Waiting can cost you thousands of dollars over time, so enrolling during your open enrollment period is the most affordable route for most people.

You can also enroll in Medigap during the annual open enrollment period from January 1 to March 31 each year, but outside your initial six-month window, insurers may underwrite your process depending on your state.

What Medigap Does Not Cover

Medigap covers gaps in Original Medicare, but it does not cover everything. Prescription drugs are not covered by any Medigap plan — you need a separate Part D prescription drug plan for that. Long-term care, dental work, vision exams, eyeglasses, hearing aids, and routine hearing exams are also not covered by Medigap.

If you travel outside the United States, Original Medicare does not cover you, and most Medigap plans do not either — though some plans offer limited emergency coverage abroad. If you need coverage for these gaps, you may need to buy additional insurance or pay out of pocket.

Medigap Versus Medicare Advantage: Which Path to Choose

When you turn 65, you have two main routes: Original Medicare with a Medigap policy, or a Medicare Advantage plan (Part C). They work very differently. With Original Medicare and Medigap, you can see any doctor or hospital that accepts Medicare, and your Medigap policy covers most of the costs Medicare does not. With Medicare Advantage, you choose a managed care plan that has a network of doctors and hospitals, and you typically pay less in premiums but more when you use care.

Medicare Advantage plans include prescription drug coverage and often include dental, vision, and hearing benefits. Original Medicare with Medigap does not include these, so you buy them separately. Medicare Advantage plans have out-of-pocket maximums; Medigap plans do not (though your Medigap premium itself is a fixed cost). The choice depends on your health, your doctors, and how much you expect to use care.

How to Compare Medigap Plans and Find Rates

Start by visiting Medicare.gov and using the Medigap plan comparison tool. Enter your state and the plans you are considering, and you will see a side-by-side chart of what each plan covers. This helps you understand the real differences between, say, Plan G and Plan N.

Next, get quotes from multiple insurance companies. You can call companies directly, use Medicare.gov's plan finder, or contact your State Health Insurance information Program (SHIP), which offers free counseling. SHIP counselors can explain the plans in your state and help you understand which one fits your situation. Rates vary widely by company, so comparing at least three is worth your time.

When you compare, look at the premium, the deductible (if any), and what you will pay out of pocket for common services like doctor visits and hospital stays. The cheapest plan is not always the best deal if it leaves you paying more when you actually need care.

Frequently Asked Questions

Can I switch Medigap plans after I enroll?

Yes, you can switch to a different Medigap plan at any time, though the new plan may require medical underwriting if you are outside your initial enrollment period and your state allows it. Some states have may provide issue rights that let you switch without underwriting during certain windows. Contact your state insurance commissioner's office or SHIP to learn what applies where you live.

Do I need Medigap if I have retiree health insurance from my former employer?

Not necessarily. If your employer coverage is comprehensive, it may cover the gaps that Medigap would. However, if your employer coverage ends or changes, you may lose the right to enroll in Medigap without medical underwriting. Review your employer plan carefully and talk to your benefits administrator before deciding.

What happens to my Medigap policy if I move to a different state?

Your current Medigap policy may not be available in your new state, and you may need to switch to a plan offered there. You typically have a may provide issue right to enroll in a new Medigap plan in your new state without medical underwriting. Contact your current insurer and your new state's insurance commissioner's office to understand your options.

Does Medigap cover care outside the United States?

Most Medigap plans do not cover routine care abroad, but some offer limited emergency coverage (typically 80 percent of costs) for the first 60 days of a trip. If you travel frequently or live part of the year outside the U.S., ask your insurer about their foreign travel coverage before you enroll.

Can my Medigap premium increase, and by how much?

Yes, premiums increase over time. The amount and frequency depend on your plan, your insurer, and your state's rules. Some increases are tied to inflation or the cost of medical care; others reflect your age. Your insurer must notify you of any rate increase before it takes effect. You can shop for a better rate with a different company each year during the annual open enrollment period.