Would it be okay to take unprescribed antibiotics when you have strep throat?

Not a good idea: You ? Have some abx left over from another illness that you didn't finish or you have some from a friend.You also do not know that you have strep by doing a confirmatory test.Treatment for strep is to prevent long term complications which requires a full treatment course. If you don't have it, you don't need to treat.If you do, the short amount you have won't stop complications.