Does Fluoxetine (Prozac) cause weight gain?
The honest answer from the FDA-approved label for Fluoxetine (Prozac)— what the trials actually reported, not the “every drug makes you gain weight” folklore.
What the label reports
The label reports weight loss, not gain. Its Altered Appetite and Weight section states that significant weight loss — especially in underweight, depressed, or bulimic patients — may be an undesirable result of treatment. In US placebo-controlled trials, weight loss was reported in 1.4% of fluoxetine-treated patients versus 0.5% on placebo (listed as an adverse reaction at 2% vs 1%), and patients treated with fluoxetine lost an average of 0.45 kg compared with a 0.16 kg gain on placebo over a 16-week double-blind trial. The label advises that weight change be monitored during therapy, and notes decreased weight gain has been observed in children and adolescents. It does not report weight gain.
Frequently asked questions
Does Fluoxetine cause weight gain?
The label's picture is above. Fluoxetine's weight effect is can cause weight loss — read the summary rather than the folklore, and track your own trend.
How much weight can Fluoxetine cause?
The label reports what the trials found (above) and does not hand out a single number that applies to everyone — weight change depends on dose, duration, your starting point, and why you are taking the drug. If your weight is changing in a way that bothers you, that is a specific, fixable conversation with your prescriber, not a reason to quit abruptly.
Does the weight come off after stopping Fluoxetine?
Often at least partly, when the drug's effect on appetite or metabolism was the cause — but that is individual, and some weight tracks lifestyle rather than the drug. Never stop a medication just to lose weight without talking to the prescriber first; for several of these drugs abrupt stopping has its own risks.
More guides for Fluoxetine
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The weight information is what the drug’s FDA-approved label reports from its trials. This is general reference information, not medical advice, and weight change is individual — do not start or stop a medication to change your weight without your prescriber.