doctor's orders
Instructions given by one's doctor. Acting upon my doctor's orders, I cleared my schedule and spent the week recuperating at home. Samantha, you need to stay off your foot and use your crutches—doctor's orders, remember?
doctor's orders something
that one is strongly advised to do as ordered or as if ordered by a doctor. I have to spend a month in Arizona. Doctor's orders. I'm doing this on doctor's orders, but I don't like it.