The prescribing information for Prozac (fluoxetine) recommends to take it in the morning, with or without meals.

Morning administration is recommended for a few reasons:

  • Prozac was dosed in the morning in the initial clinical trials for the drug, and effectiveness/side effect data is based on that.

  • Insomnia is a common side effect of Prozac, with some studies reporting an incidence rate as high as 33%. Taking it in the morning is thought to decrease the risk of sleeping problems.

Per the prescribing information:

"In controlled trials used to support the efficacy of fluoxetine, patients were administered morning doses ranging from 20 to 80 mg/day. Studies comparing fluoxetine 20, 40, and 60 mg/day to placebo indicate that 20 mg/day is sufficient to obtain a satisfactory response in major depressive disorder in most cases. Consequently, a dose of 20 mg/day, administered in the morning, is recommended as the initial dose."
Prozac Package Insert

While taking Prozac in the morning is recommended, it is important to know that sedation is also a fairly common side effect of the drug, occurring in 5-10% of individuals.

If Prozac does make you tired, taking it at bedtime may be a better option. There is no data to indicate that evening administration makes it less effective.

All in all, deciding what time to take Prozac will largely be based on what is most convenient for you and the side effects you may (or may not) experience.

Answer Summary

Morning administration is generally recommended when first starting Prozac (fluoxetine). However, dosing in the evening is an option to mitigate sedative side effects should they occur.

About Prozac

Prozac (fluoxetine) is a selective serotonin re-uptake inhibitor (SSRI) and is most commonly used for the treatment of major depressive disorder. It is also used to treat panic disorders, bulimia, OCD (Obsessive Compulsive Disorder) and PMDD (premenstrual dysphoric disorder).

Prozac works by increasing the amount of the neurotransmitter serotonin in the brain. Like all antidepressant medications, effects of the drug typically take 4-6 weeks to be realized.

Prozac is associated with a number of potential side effects, including:

  • Weight fluctuations (gain and loss)
  • Headache
  • Sedation
  • Insomnia
  • Dizziness
  • QT prolongation
  • Sexual dysfunction

If you need to discontinue Prozac, it is recommended to slowly taper the medication to avoid withdrawal reactions. However, Prozac has an extremely long half-life, around 4 to 6 days, and is associated with fewer withdrawal reactions than most other antidepressants with shorter half-lives.

  1. Prozac Prescribing Information. GSK
  2. Fluoxetine: a review on evidence based medicine. PubMed