With all the details, options and deadlines surrounding Medicare Prescription Drug Plans (PDPs), it's no wonder that people are confused.

If you're like a lot of seniors, you might have enrolled simply to beat the May 15 deadline, whether or not you understood what you were signing up for.

Now, you might feel stuck. If you fall into one of several categories, you might not be stuck after all; in fact, if you are already enrolled in regular Medicare (i.e. Parts A and B) and have also already enrolled in a Medicare Part D Prescription Drug Plan, it's not too late to switch your Medicare coverage.

If you currently have a Medicare Advantage plan that includes prescription drug coverage, you can switch to another Medicare Advantage prescription drug plan, or you can enroll in original Medicare and a Part D PDP.

However, you cannot switch to a Medicare Advantage plan that does not provide Medicare prescription drug coverage.

If you currently have a Medicare Advantage plan that does not provide prescription drug coverage, you can switch to another Medicare Advantage plan without prescription drug coverage.

However, you cannot switch to a Medicare Advantage plan that includes prescription drug coverage. You may also switch to original Medicare, but you cannot enroll in a Medicare Part D PDP.

If you currently have original Medicare in addition to a Medicare Part D PDP, you may switch to a Medicare Advantage prescription drug plan.

However, you cannot switch to a different Medicare Part D PDP or to a Medicare Advantage plan without prescription drug coverage.

Another tricky situation arises for people who are new to Medicare Advantage plans. If this is your first time enrolling in a Medicare Advantage plan with prescription drug coverage, you can "voluntarily disenroll" within the first 12 months of coverage.

If you do this, you will have a special enrollment period that allows you to get original Medicare (Parts A and B) and a Medicare Part D PDP or join a different Medicare Advantage plan with prescription drug coverage.

This may seem confusing, but the Senior Health Insurance Information Program (SHIIP) is available to help.