How long should fluoxetine side effects last?

Depends. The common initial side effects of fluoxetine (dry mouth, upset stomach, nausea, constipation or diarrhea) should go away after two weeks. If they persist, let your doctor know. Other side effects like blurred vision, sweating, sexual side effects can also fade over time, but again, if they last more than two weeks or affect you adversely, talk to you doctor.