If you are eligible for Medicare Part B medical insurance, but you didn’t sign up for it when you first became eligible for Medicare, you will have another opportunity to apply.

Open season for Medicare Part B runs from Jan. 1 until March 31, 2009. Better to act early than late - if you miss the deadline, you will have to wait until 2010 to apply. Medicare Part B covers some medical expenses not covered by Medicare Part A (hospital insurance), such as doctors’ fees, outpatient hospital visits, and other medical services and supplies.

When you first become eligible for hospital insurance (Part A), you have an initial enrollment period of seven months in which to sign up for medical insurance (Part B). After that, you have to pay a higher premium – unless the reason you declined Part B was because you were covered through an employer’s group health plan or a group health plan based on a spouse’s employment.

You are given another opportunity to enroll in Part B during the general enrollment period, from Jan. 1 to March 31 of each year. But each 12-month period that you are eligible for Medicare Part B and do not sign up, the amount of your monthly premium increases by 10 percent.

Medicare is made up of four parts:

• Hospital insurance (Part A) that helps pay for inpatient care in a hospital or skilled nursing facility (following a hospital stay), some home health care and hospice care;

• Medical insurance (Part B) that helps pay for doctors’ services and many other medical services and supplies that are not covered by hospital insurance;

• Medicare Advantage (Part C) plans are available in many areas. People with Medicare Parts A and B can choose to receive all of their health care services through one of these provider organizations under Part C; and

• Prescription drug coverage (Part D) that helps pay for prescription medications.

In addition, some people with limited income and resources may qualify for extra help to pay for the costs - monthly premiums, annual deductibles and co-pays -related to their Medicare prescription drug plan (Part D). You can learn more about the extra help at www.socialsecurity.gov/prescriptionhelp. You can learn more about Medicare by reading our electronic booklet, Medicare at www.socialsecurity.gov/pubs/10043.html. You also can call toll-free at 1-800-772-1213 (TTY 1-800-325-0778) to ask for a copy. Or visit the Medicare website at www.medicare.gov. You also can call Medicare at 1-800-MEDICARE (1-800-633-4227; TTY 1-877-486-2048).

R. Andrew Hudson is a Social Security public affairs specialist in Helena.