Only when you can. Be sure that the medication is the cause. Were you tired or prone to be tired before starting the prozac (fluoxetine)? Have you checked with your physician to see if there are possible medical issues that could cause tiredness. If the tiredness came after starting the prozac (fluoxetine), how soon after? If occuring early on it could be the medication or not enough time to clear tiredness from depression. Wait it out.