Q. What is Medigap insurance? Do I need it?

A. Medicare supplemental insurance is not part of the Medicare program. It is private insurance you can purchase separately, for an additional premium, to cover some or most of your out-of-pocket costs if you’re enrolled in the traditional Medicare program. That’s why it’s often called “Medigap.”

You can buy one of 10 standardized Medigap policies. Each policy is labeled with a letter of the alphabet — A, B, C, D, F, G, K, L, M, N — and offers a different range of benefits from the others. All policies include coverage for certain core benefits, such as copays for Part B services and extended stays in the hospital. For example: Medicare pays 80 percent of a doctor’s bill and your share is 20 percent. Medigap pays your share and you pay nothing.  Some policies provide more benefits — for example, covering additional out-of-pocket costs in Medicare and emergency medical treatment abroad.  Generally: the greater the coverage, the higher the premium.

If you’re age 65 or older and buy a Medigap policy within six months of enrolling in Part B, you get full federal guarantees and protections.  This means that a Medigap insurer cannot turn you down or charge a higher premium because of current or past health problems and must cover preexisting medical conditions. (However, an insurer may delay coverage of treatment for a preexisting condition for a period, typically six months, after purchase. Some state laws give additional consumer protections in this regard.)  

There are several other situations in which you’re entitled to these protections — such as losing employer health coverage, COBRA or retiree benefits that serve as secondary coverage to Medicare, or if you’re enrolled in a Medicare Advantage plan that closes down or you move out of its service area.  In these circumstances, the time frame for buying a Medigap policy is about two months.

If you’re under 65 and have Medicare due to disability, these federal guarantees do not apply, although some states have similar protections. See related article: “Getting Medigap Insurance Under Age 65.”

Things to remember when considering Medigap insurance

• You pay a premium for Medigap in addition to your Medicare Part B premium — Medigap doesn’t cover that premium.
  
  
• You can use Medigap only to cover out-of-pocket costs in the traditional Medicare program. You can’t use it if you’re enrolled in a private Medicare health plan. (For the differences between traditional Medicare and Medicare Advantage plans, see a related article, “Explaining Medicare Options.)
  
  
• You can’t use Medigap to cover out-of-pocket costs for outpatient prescription drugs, unless you’re still using an H, I or J policy that dates from before 2006. (The law prohibited insurers from selling new Medigap policies that cover prescription drugs after the Medicare Part D drug benefit became available.)
  
  
• You can generally use Medigap to cover the out-of-pocket costs specified in your policy when obtaining Medicare services from any doctor, hospital or other provider anywhere in the country. However, if you buy a type of policy called “Medigap SELECT” — which typically has a lower premium than most Medigap policies — it covers your bills only when you go to providers in its network, except in an emergency.
  

For more detailed information, see the Medicare publication “Choosing a Medigap Policy.”

Next: Comparing Medigap policies. »