It’s one of the most common complaints about Medicare drug plans: A patient goes to the drugstore to pick up a prescription, only to find out the drug plan won’t cover it. Here’s what to do if it happens to you.

By law Part D plans won’t pay for certain types of drugs, period. These include medications for baldness, erectile dysfunction, obesity, wrinkles, and infertility. For those, you’ll have to pay out of pocket. Use GoodRx.com to find the best prices.

For any other rejection, the drugstore is supposed to hand you a standardized notice saying it can’t fill your prescription and to contact your plan and/or prescribing doctor for more information. However, according to the Medicare Rights Center, a nonprofit consumer advocacy group, almost none of the people who’ve contacted them about prescription denials have any recollection of ever getting this piece of paper.