Medicare prescription drug plans can change which drugs they cover, possibly leaving you without coverage for a drug you need. Or you might switch plans, and find that your new plan doesn’t cover your medication at all. In these circumstances, it’s good to know that Medicare drug plans are required to offer you a 30-day transition supply of the drug you’re taking.

All Medicare Part D plans must offer these transition refills, including Medicare Advantage plans with prescription drug coverage. Plans must provide a 30-day supply of an ongoing medication (unless a lesser amount is prescribed) within the first 90 days of plan membership or within the first 90 days of the new contract year.

Plans are also required to provide written notice that you’re using your transition supply, and explain in writing what your rights are.

You’re entitled to a transition refill when you first enroll in a Part D plan, when you move to a new plan that doesn’t cover your current medication, when your current plan drops your medication or imposes new restrictions on the drug, or when you experience a change in your level of care (such as a move from a hospital to a nursing home).

The 30-day supply is designed to give you time to talk to your doctor about substitute medication or request a coverage exception from your current plan. If you ask for a coverage exception, your plan must provide temporary refills until the request has been processed.

Residents in long-term care facilities get additional protections. If you’re in a long-term care facility, your plan must cover all the 30-day refill requests you submit in the first 90 days on the plan. After the first 90 days, the plan must offer an emergency 30-day supply if your request for an exception has not yet been processed.