1. Literally, not taking one's prescribed medications. I've been able to think more clearly after going off my meds—my mind doesn't feel as foggy. I knew as soon as she walked in that she was off her meds—she never acts that way when she's on her regimen.

2. Crazy or insane. Potentially offensive due to the implication of mental illness. She's off her meds if she thinks she can come in here and talk to me in that tone of voice! When Paul suddenly decided to pick up and move across the country, everyone said he must be off his meds.