If you signed up for Medicare Part D last year and think you’re all set, think again.

Less than a year after starting a prescription drug program for seniors and the disabled, the federal government is holding a six-week open enrollment for people who were eligible but didn’t sign up before. For thousands of people who are already enrolled, Nov. 15 to Dec. 31 is also the only time they’ll be able to switch drug plans.

And because of changes in Maine’s rules, changes in plans and changes in individual health needs, some Mainers will want to switch. Some must switch.

“You don’t have a lot of time to make a big decision,” said Jude Walsh, head of prescription drug programs for the Governor’s Office of Health Policy and Finance.

Medicare Part D started Jan. 1 to provide prescription drug plans to millions of Americans. The program immediately floundered under a tide of computer glitches and enrollment problems. Within days, Maine began picking up the tab for thousands of people who couldn’t get what they needed from the federal program. It spent more than $10 million over several months.

Part D’s problems have since abated.

About 125,000 Mainers are now enrolled in Part D, according to Centers for Medicare and Medicaid Services.

Thousands of Mainers won’t have to do anything during the Nov. 15 to Dec. 31 open enrollment period. Some are allowed to switch plans throughout the year and can ignore open enrollment. Some have plans that will still work for them in 2007, and they won’t want to switch.

But other Mainers will have to make changes:

• Nearly 17,000 will be automatically switched to a new plan because they get state help with premiums and their current plan’s premiums are rising higher than allowed.

• Some will find their plans are no longer offered in Maine.

• Some – no one knows how many – will find their current plan no longer meets their needs, either because the plan will change for 2007 or because their drug needs are changing.

For questions or help switching plans, call the federal hotline at 1-800-MEDICARE or the state hotline at 1-866-RX-Maine. Mainers can also get help from Legal Services for the Elderly at 1-800-750-5353 and their local Area Agency on Aging. Mainers have until Dec. 31 to switch plans, but the federal government is encouraging people to get everything done by Dec. 8 so there’s enough time to ensure a smooth changeover Jan. 1.

“It’s like learning everything new again,” Walsh said.