What Do Frequent Urination And Headache Post Intake Of Antibiotics Mean?

About 2 weeks ago my husband went to the emergency room for an abcess in his chin. He has successfully finished taking both antibiotics but soon after got a fever and said his upper arms felt weird. The fever has since gone away but he is not complaining of frequent urination and a headache. (He is worried he is becoming dehydrated because he is going so often).