It's a government program that pays some or all of your out-of-pocket drug costs if you have Medicare drug coverage. Eligibility is based on your monthly income and assets.

You're responsible for paying your monthly premium, deductible and copays.

• Your premium is the monthly fee for plan coverage.
• A deductible is how much you must pay yearly for medications before a plan begins to pay its share.
• A copay is the amount of the drug's cost that you're responsible for after your deductible is met. Copays vary based on medication.

The best time to sign up for drug coverage is during your Medicare Initial Enrollment Period. This is the seven-month period when you're first eligible for Medicare. You could also add a prescription drug plan during the following:

• Medicare Annual Enrollment Period, or AEP – Each year, the AEP runs from Oct. 15 through Dec. 7. You can join or switch a prescription drug plan during this time. Special circumstances like moving out of your plan's coverage area or losing coverage may allow you to enroll or make changes outside of the AEP.
• Medicare Advantage Open Enrollment Period – Runs from Jan. 1 through March 31 of each year. During this time, you can disenroll from a Medicare Advantage Plan to enroll in a new one. You can also disenroll to go back to Original Medicare. In either case, you can add a stand-alone Part D plan to the coverage.