How long does it take for flouxitine to work?

Fluoxetine activity. Fluoxetine enhances serotonin levels in the brain. Serotonin is a brain chemical involved in mood regulation. For this medication to be effective it must be taken on a daily basis. Usually it will take from 2-4 weeks to notice any improvement. A follow-up with your physician is important. At times the dosage may need adjustments, or a a different medications may be required.