En español | If you have Medicare Part D prescription drug coverage, the chances are very high that this year you've been paying a lot more for your medications than you needed to.

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That's because so few enrollees bother to compare the Part D drug plans available to them. As a result, in 2011 fewer than 7 percent are in the Part D plan that offers them the lowest out-of-pocket costs, according to a recent analysis.

Comparing plans during open enrollment is the best way to ensure that you don't miss out on your best deal for 2012, which could produce savings of several hundred dollars next year, especially if you take a lot of medications.

But be warned: This year's seven-week open enrollment period begins Oct. 15 and ends at midnight on Dec. 7 — a deadline three weeks earlier than in previous years.

If you enroll in a different plan during this period, coverage in your current plan will automatically end at midnight on Dec. 31 and your new coverage will begin Jan. 1.

If you choose to keep your current plan (and it is still offered in 2012), you don't need to take any action — your enrollment automatically continues next year.

Medicare Part D prescription drug plans in 2012

All Part D plans can change their costs and coverage each calendar year. So pay attention to the "Annual Notice of Change" you should have received from your current plan in September. This spells out any changes for 2012 — in premiums, deductibles, copayments or coverage — and may contain good news or nasty surprises.

Among "stand-alone" Part D drug plans — the kind you have if you're enrolled in traditional Medicare rather than a Medicare Advantage plan — a few that operated in 2011 will no longer be available in some states in 2012.

If you're in one of these plans, you may be automatically enrolled in another offered by the same insurance company, if available, or you can switch to a different plan. There are still plenty of choices in each state, ranging from 25 in Alaska and Hawaii to 36 in Pennsylvania and West Virginia.

Overall, monthly premiums for stand-alone plans in 2012 will range from $15.10 to $131.80. On average, premiums will fall slightly, according to the Centers for Medicare & Medicaid Services. But some premiums will rise significantly.

For example, the country's most popular drug plan, AARP MedicareRx Preferred, run by UnitedHealthCare, will increase its monthly premiums by an average of 14 percent, ranging from 20 cents in Arizona to $8.10 in California. UnitedHealthCare spokesman Matthew Burns says that the plan "covers more branded drugs than most of our competitors and has no deductible," adding that on average "our premiums for 2012 are slightly lower than 2010 levels," given that they fell in most states in 2011.

Next: Medicare Advantage plans in 2012. >>