A Medicare supplement insurance policy (Medigap) can help pay for some of the health care costs that Original Medicare doesn't cover, such as when you travel outside the US, copays, coinsurance, and deductibles. If you have Original Medicare and you buy a Medigap policy, Medicare will pay its share of the Medicare-approved amount for health care costs. Then your Medigap policy pays its share.

Have your red, white and blue Medicare ID card ready when you enroll. If you don't have such a card available, contact the Social Security Administration (SSA) at 469-777-2123 (TTY). Ask SSA for the name on your records and the effective dates of Medicare Parts A and B. Before you begin, make sure you have this information: Postal Code, Medicare number, your Last Name and Date of Birth.

A Medicare supplement insurance plan helps cover unpaid costs after Medicare Parts A and B pay their share of your health care expenses. Unlike a Medicare Advantage plan (which is an alternative to your Medicare Parts A and B benefits) you buy a Medicare supplement plan in addition to your Medicare Parts A and B benefits.

Part A covers inpatient hospital care or a limited stay in a skilled nursing facility. Part B covers outpatient hospital and medical services. The premium you pay for Part B is deducted from your Social Security benefits. Medicare pays for many health care services and supplies, but it does not cover all of your health care costs. For example, you pay a deductible for each hospital stay and coinsurance each time you use the services of a doctor or surgeon.