It takes 4 to 8 weeks for antidepressants like Prozac to take full effect. As such, you can expect Prozac to stay in your body for several days after use.
The exact timeline for medications staying in your body varies, even among SSRIs. Prozac can take 25 days or longer to fully exit your body.
You shouldn’t suddenly stop taking Prozac or change your dose. This may lead to withdrawal symptoms and decrease the overall efficacy of your medication. If a doctor recommends that you stop taking Prozac, they'll let you know how to do it gradually.