Medicare Supplement Insurance

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Medicare supplement insurance (Medigap) helps pay some of the out-of-pocket health care costs that Original Medicare (Parts A and B) doesn’t pay. It isn’t a government benefit, like Parts A and B. Plans are offered through private insurance companies. It’s your decision whether to buy a plan or not.

There are 10 standardized Medicare supplement insurance plans, labeled “A” through “N.” (These letters are not related to the Medicare Part A, B, C and D labels.) The plans and what they cover are prescribed by the federal government.

What Does Medicare Supplement Insurance Cover?

The main purpose of a Medicare supplement plan is to cover some of the out-of-pocket costs not paid by Medicare Parts A and B, like deductibles, co-pays and co-insurance. Each of the standardized plans provides benefits for different out-of-pocket costs.

Each standardized plan with the same letter must offer the same basic benefits, no matter which insurance company sells it. For example the basic benefits of one company’s Plan F are the same as the basic benefits of another company’s Plan F. The only difference between Medicare supplement plans with the same letter sold by different insurance companies is usually cost.

What do Medicare Supplement Insurance Plans Help Cover

Do you live in MA, MN or WI?

Medicare supplement insurance is standardized differently in Massachusetts, Minnesota and Wisconsin. Call your State Health Insurance Assistance Program (SHIP) for information.

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What Does Medicare Supplement Insurance Cost?  

The table shows the types of costs you may have with a Medicare supplement insurance plan. You need to look at individual plans to understand their specific costs.

Type Description
Premium  Plan premiums can vary from company to company, even for exactly the same coverage. You continue to pay the Part B premium to Medicare as well. 
Deductible You may pay Part A and Part B deductibles with some Medicare supplement plans. The high-deductible Plan F has an annual plan deductible. 
Co-payment  You may pay a set co-payment for covered Part B services with some Medicare supplement plans. 
 Co-insurance You may pay part of the co-insurance amount for covered Part B services with some Medicare supplement plans. 
How Medicare Supplement Insurance Works

Each standardized Medicare supplement insurance plan covers different types of out-of-pocket costs. So what you pay in out-of-pocket costs will depend on what services you use and which plan you have.

This is a little confusing, so let’s use an example. 

Suppose a person has Original Medicare (Parts A and B) and receives the following covered services: 

  • 15 days as an inpatient in the hospital
  • 22 days in a skilled nursing facility
  • 2 visits with a doctor who doesn’t accept Medicare assignment

The table below compares what the person's out-of-pocket cost for these services might be with different Medicare supplement insurance plans. This example assumes that the Part B deductible is met for the year. The costs shown are for illustration only. Actual costs may be different.

  No Plan Plan A Plan C Plan F
Part A deductible for the benefit period  $1,364 $1,364 $0 $0
Part A co-insurance for skilled nursing facility over 20 days (2 days x $170.50)  $341 $341 $0 $0
Part B co-insurance for 2 doctor visits (20% of Medicare-approved amount) $32 $0 $0 $0
Part B excess charges for same doctor visits (15% of reduced Medicare-approved amount)

$24 $24 $24 $0
Total out-of-pocket cost  $1,761 $1,729 $24 $0

So depending on which Medicare supplement insurance plan the person in this example has, some or all of their out-of-pocket costs could be covered. In general, plans that cover more costs have higher premiums.

Medicare supplement insurance or Medicare Advantage?

Each may help you manage out-of-pocket health care costs, but in different ways.

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Enrolling in a Medicare Supplement Insurance Plan

You have a specific enrollment period for Medicare supplement insurance called the Medicare Supplement Open Enrollment Period. This period:

  • Begins the first month that you are age 65 or older and enrolled in Medicare Part B
  • Lasts for 6 months
  • Guarantees your right to buy a plan (You cannot be denied coverage if you apply during this period.)
Medicare Supplement Open Enrollment Period

Even if you miss your open enrollment period, you may apply for Medicare supplement insurance at any time. You could be denied coverage, though, or charged a higher premium based on your health history. Some states have additional Medicare supplement open enrollment periods, including for beneficiaries under age 65.