To get Medicare drug coverage, you must sign up for one of the private drug plans approved by Medicare. You have many to choose from — all with different costs and benefits — wherever you live.

In most cases, the plan you choose will be the one you have to stay in for the entire calendar year (or the rest of the year if you’re new to Medicare and joining a plan partway through the year). So it’s wise to compare plans carefully to find the one that best meets your needs. Even if you’re already in Part D, making a careful comparison between the plan you have now and alternatives available to you for next year is the only way to ensure that you continue to receive the best deal for you.

How can I find out what different plans offer?

You will receive many promotions from Medicare drug plans in your area. The plans available to you are also listed at the back of the official “Medicare & You 2010” handbook that you receive in October. But neither the marketing promotions nor the handbook provides enough details to make an informed decision. To make a real choice and find the plan that suits you best, you need to compare plans point by point, as explained below.

How can I pick just one plan from so many choices?

You need to compare them according to the drugs that you take. It’s the specific drugs you take (and not the amount of the premiums or deductibles) that most determines what you will spend out of pocket under any plan. (In fact, the plans vary enormously in the copays they charge, even for the same drug. In some cases, the same drug can cost more than $100 for a 30-day supply in one plan than in another.) The most effective way to make a comparison is to use the online tool on Medicare’s website.  Click on “Find health and drug plans” on the home page. Then enter your Zip code and the exact names of all the drugs you take, their dosages and how frequently you take them. The results will show which plans cover your drugs and your likely out-of-pocket expenses, month by month through the whole year.

You can also call the Medicare hotline at 800-633-4227 and ask a customer service representative to do a similar search and send you the results by email or regular mail.

I’m already in a Part D plan that suits me. Why should I bother comparing plans again at the end of the year?

Because the plan that’s best for you this year might not be the best next year. Part D plans can change their costs and benefits every year, and most do. These changes may include premiums, deductibles, copays, the drugs they cover and whether they offer any coverage in the doughnut hole.

In September, look for an important letter from your plan headed “Annual Notice of Change.” Read it carefully for details of how your plan will change next year. (The plan must get this notice to you by September 30. If you haven't received it by then, call the plan and ask for it. If it still doesn't arrive, call Medicare at 800-633-4227 to file a complaint.)

To ensure that you get your best deal next year — a plan that covers all your drugs at the least cost and with fewest restrictions — you should carefully compare the plans available to you for next year during the open enrollment period from October 15 through December 7. Ideally, make a search through the Medicare Prescription Drug Plan Finder, as explained above.