Medication Guide
Prozac (Fluoxetine): Uses, Side Effects & What to Expect
Fluoxetine — sold as Prozac — is one of the original and most widely used SSRIs. It treats depression, OCD, panic disorder, bulimia, and PMDD. It has an unusually long half-life, which often makes missed doses and stopping gentler than with other SSRIs. Early effects can appear in 1–2 weeks; the full mood benefit usually takes 4–6 weeks.
Clinically reviewed by the Lyte Psychiatry Clinical Team · Last reviewed June 2026
What is fluoxetine?
Fluoxetine is a selective serotonin reuptake inhibitor (SSRI). It increases the amount of serotonin — a chemical messenger tied to mood — available between nerve cells in the brain. It’s sold as Prozac and widely as a generic, and it’s known for a long half-life that keeps working in the body for some time after a dose.
What does Prozac treat?
Fluoxetine is FDA-approved for major depressive disorder (including in children 8 and older), obsessive-compulsive disorder (OCD), panic disorder, bulimia nervosa, and premenstrual dysphoric disorder (PMDD). It’s also used in combination with another medication for certain treatment-resistant and bipolar depression.
How long does it take to work?
Some early effects — better sleep, appetite, or steadier anxiety — can show up in the first one to two weeks, while the fuller benefit for mood usually builds over four to six weeks. Fluoxetine can be a bit activating, so some people feel more energized (or jittery) early on.
Common side effects
Most side effects are mild and ease with time. The most common include:
- Nausea or reduced appetite
- Trouble sleeping
- Headache
- Dry mouth
- Feeling jittery or restless early on
- Sexual side effects (such as lower libido)
Reach out if anything is bothersome rather than stopping on your own.
A note on dosing
Dosing is individualized by your prescriber based on your diagnosis, age, other medications, and response. This page intentionally doesn’t give a specific number — the goal is the lowest effective dose, adjusted with your clinician.
An important safety note
Like all antidepressants, fluoxetine carries an FDA “boxed warning”: in children, teens, and young adults under 25, antidepressants can in rare cases increase suicidal thoughts, especially early in treatment or after a dose change. Close early follow-up is how we manage this. If you or someone you love has thoughts of self-harm, call or text 988 (the Suicide & Crisis Lifeline) right away.
Stopping fluoxetine
Because of its long half-life, fluoxetine tends to cause fewer discontinuation symptoms than many antidepressants — but it’s still best to stop with your prescriber’s guidance rather than abruptly.
Frequently asked questions
What is Prozac (fluoxetine) used for?
Fluoxetine (brand name Prozac) is an SSRI antidepressant FDA-approved for major depressive disorder, OCD, panic disorder, bulimia nervosa, and PMDD. It is also used in combination for certain treatment-resistant and bipolar depression.
How long does Prozac take to work?
Early effects can appear within 1 to 2 weeks, while the full benefit for mood usually takes 4 to 6 weeks. Keep taking it as prescribed even if the first weeks feel slow.
What are the common side effects of fluoxetine?
Common side effects include nausea, reduced appetite, trouble sleeping, headache, dry mouth, feeling jittery, and sexual side effects. They are usually strongest early and ease with time.
Is Prozac addictive?
No. Fluoxetine is not a controlled substance and is not addictive. Because of its long half-life it often causes milder discontinuation effects than other SSRIs, but you should still stop with your prescriber's guidance.
Why is Prozac's long half-life important?
Fluoxetine stays in the body longer than most SSRIs. This can make occasional missed doses less disruptive and tends to make stopping gentler, since the medication tapers itself somewhat.
Can I drink alcohol while taking Prozac?
It is best to avoid or limit alcohol, since it can worsen drowsiness and dizziness and work against the benefits for mood. Talk with your prescriber about what is right for you.
Related pages
This page is for general education and is not medical advice or a substitute for care from your own clinician. Medication decisions should always be made with a licensed prescriber who knows your history.
Wondering if Prozac is right for you?
Our Texas psychiatry team can review your symptoms, history, and goals and build a plan that fits — with close follow-up. Same-week appointments available.
Book an appointment