Have you figured out exactly how Medicare Part D works yet? Many people who receive Medicare have found this recently added prescription drug benefit from the Federal government more than a little confusing. Some seniors still do not fully understand its complexities nearly three years after it went into effect in January 2006.

Medicare Part D allows you to get part of your prescription drugs paid through insurance, no matter what your income, illnesses, or drug costs. You are eligible for this program if you are eligible for Medicare, which you can join during the three months before or three months after your 65th birthday. Then you can sign up or switch plans during open enrollment each year — between Nov. 15 and Dec. 31. Your new coverage begins on Jan. 1 of the following year. If you sign up after open enrollment, you may have to pay a penalty.

Coverage for Medicare Part D is set up by private insurance companies. There are two main types of Medicare plans:

n Medicare Prescription Drug Plans. These cover prescription drugs only.

n Medicare Advantage Plans with Prescription Drug coverage. These cover both medical care and prescription drugs. Examples include health-maintenance organizations, preferred-provider organizations, or private fee-for-service plans.

As you make your choice, consider whether you only need prescription coverage or you need it combined with medical care.

Each plan has a list of the drugs it covers, how much you pay for each one, and any limits to getting a particular drug. This list is called a formulary. Write down a list of all the drugs you take, and then pick a plan that covers most of them. If one of your medications is not on the list, you may have to pay full price, switch to a similar drug, or apply for an exception.

You can compare plans at www.medicare.gov using the Web site's Prescription Drug Plan Finder. Or, call the Medicare at 1-800-MEDICARE to get your local State Health Insurance Assistance Programs (SHIP) number. Pick two or three plans for a closer look, and then contact each plan for more information.

As for the cost involved, it's a bit of a Rubik's cube to decipher. Of course, it varies, depending on the plan you choose. However, most plans charge a monthly premium of about $28, with a $275 deductible and co-pay for each drug. If you think you qualify for financial help, contact the Social Security Administration at (800) 772-1213. You may qualify if you have an income of $15,315 or lower ($20,535 for a couple).

If you don't qualify for extra help, your plan may include a "coverage gap," which is sometimes called a "doughnut hole." Here's how it works: After you and your plan have spent $2,510 on prescription drugs, you have to pay all of the next $3,216 prescription drug costs yourself. Once that is paid, you have what's called catastrophic coverage, where you pay only a small amount for the rest of the year.

Need more information? Your friendly neighborhood pharmacist will be glad to answer your questions. Or you can consult the National Council on Aging Web site at www.mymedicarematters.org and the official Medicare Web site at www.medicare.org/.

Ed Clark can help you decipher the puzzle of Medicare Part D at the Webster Pharmacy, where he is the proprietor and licensed pharmacist. Ply him with clues at 1553 Webster St. in Alameda.