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Prozac (Fluoxetine) Side Effects: A Complete Guide

Kristin Hall

Reviewed by Kristin Hall, FNP

Written by Geoffrey C. Whittaker

Published 07/22/2020

Updated 08/17/2023

Prozac: the OG antidepressant — the one that started it all. As it approaches its fourth decade on the market, brand-name Prozac (and its generic fluoxetine) is still among the most prescribed selective serotonin reuptake inhibitors (SSRIs) currently available. 

Unfortunately, like many things from the ’80s, time has revealed some unpleasant facts about Prozac.

They aren’t necessarily deal-breakers, but there’s a list of unpleasant side effects users might expect to grapple with in their first weeks or months of taking fluoxetine — or potentially for the duration of their treatment. 

Are you worried about the side effects of Prozac? Don’t be.

Below, we’ll outline what to expect, what to worry about, and how to reduce, manage and overcome any side effects this antidepressant medication throws your way.

Fluoxetine is approved by the U.S. Food and Drug Administration (FDA) to treat several conditions, including: 

  • Major depressive disorder (MDD)

  • Premenstrual dysphoric disorder (PMDD)

  • Obsessive-compulsive disorder (OCD)

  • Bulimia nervosa and other eating disorders

  • Anxiety types like panic disorder (characterized by panic attacks)

When used in conjunction with other drugs, it may also be used to treat bipolar disorder and treatment-resistant depression. Unfortunately, for everyone taking this medication, side effects are a real risk.  

Whether you’re taking Prozac for anxiety, PMDD or even depression, the side effects don’t differ. In fact, the main factor in side effect risk is dosage. A higher dose puts you at a higher risk of experiencing side effects. 

Below, we’ll share the most common, uncommon and more serious side effects. Let’s look at each group in more detail.

Most Common Side Effects of Fluoxetine

After getting fluoxetine and starting treatment, you can generally expect to experience the common side effects of fluoxetine within one to two weeks of your first dose.

Likewise, it can take four to six weeks for the side effects to dissipate as the medication concentrations stabilize in your body.

The most common adverse effects occurring in 5 percent or more of people include: 

  • Strange dreams 

  • Nervousness or anxiety

  • Loss of appetite or changes in eating habits

  • Weight gain

  • Diarrhea or indigestion

  • Nausea

  • Dry mouth 

  • Insomnia (trouble sleeping)

  • Fatigue, sleepiness, drowsiness, tiredness or yawning

  • Weakness

  • Sexual side effects like decreased sex drive and delayed ejaculation

  • Skin rash or hives

  • Sweating 

  • Tremors

There are less common and more severe side effects to look out for too. We’ll go over these below.

Less Common Side Effects of Prozac

Among the less common side effects of Prozac are a number of more intense reactions. A significantly smaller number of users might experience:

  • Allergic reaction

  • Seizures

  • Photosensitivity

  • Paranoid delusions

  • Gynecological bleeding

  • Bloody diarrhea

  • Ulcers

  • Suicidal thoughts or suicide attempts

Contact your healthcare provider if you experience any of these.

Serious Fluoxetine Side Effects

More serious side effects can occur if you abruptly stop taking the medication. And for younger children, there’s an FDA black box warning about suicidal ideations.

It’s crucial to have open communication with your provider if you experience any side effects.

Serious and potentially life-threatening side effects of fluoxetine may include:

  • Trouble breathing

  • Eye pain or exacerbated glaucoma

  • Internal bleeding

  • Irregular heartbeat

  • Suicidal thoughts

If you experience any of these, seek immediate medical attention.

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Are There Long-Term Side Effects of Prozac?

Long-term side effects of Prozac use are uncommon. Still, there are some questions about the long-term risks of these medications that remain unanswered.

Meanwhile, overdose can lead to numerous problems, including serotonin syndrome and sudden increases in blood pressure. Withdrawal can come with uncomfortable side effects, too, so consider tapering off the medication if you think you’re ready to stop taking Prozac.

You’ll want to consider other medications as well when taking fluoxetine. Drugs that can increase these risks and cause harmful drug interactions when taken in conjunction with fluoxetine include:  

  • Monoamine oxidase inhibitors (MAOIs)

  • Non-steroidal anti-inflammatory drugs (NSAIDs)

  • Drugs that act on your central nervous system

  • Antipsychotics

  • Benzodiazepines

  • Amphetamines

  • Tryptophan

  • St. John’s wort

You’ll want to make sure your healthcare provider knows if you’re taking any of these medications as well:

  • Olanzapine

  • Thioridazine

  • Alprazolam

  • Buspirone

  • Lithium

  • Linezolid

  • Isocarboxazid

  • Tramadol

  • Pimozide

  • Phenelzine

  • Tranylcypromine

  • Warfarin

If you’re feeling a little overwhelmed, anxious or outright scared at the lists you’ve just scanned, here’s good news: Prozac side effects are overwhelmingly manageable, especially if you take certain precautions. 

To make sure you don’t bring on more risk than necessary, remember the following when taking Prozac or fluoxetine:

  • Know your Prozac dosage and stick to it — don’t risk ​​overdose by taking more meds.

  • Likewise, don’t skip doses and create withdrawal symptoms. Don’t stop your medication abruptly unless instructed by a healthcare provider. If you miss a dose, just take the next dose on time.

  • Be aware of interactions Prozac may have with other drugs. Also, be careful when combining Prozac and alcohol

  • Since Prozac can enter human breast milk, be cautious of using Prozac while breastfeeding. And if you’re breastfeeding, pregnant or trying to conceive, make sure to discuss this with your healthcare provider, as they may want to hold off on prescribing an antidepressant or make changes to your treatment plan. 

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Getting help for depression can be hard. When you’re depressed, everything is hard. 

Getting out of bed can seem insurmountable. And if your medication brings side effects, it can seem like there’s just no hope. The good news is that this side-effect-heavy treatment isn’t your only option.

Feeling stuck? Here’s what to keep in mind:

  • Side effects of taking fluoxetine are generally mild, arrive one to two weeks after starting treatment, and usually dissipate over the first four to six weeks as you adjust to the medication.

  • Other medications or medical conditions can increase your risk of adverse events when taking fluoxetine. So tell your healthcare provider about all medications you’re on — including over-the-counter drugs and supplements — as well as your medical history. 

  • If problems like sexual dysfunction and other side effects continue worsening, contact your healthcare provider right away to rule out a serious adverse reaction.

Whether you’re currently experiencing side effects or worrying about them ahead of time, reaching out to a healthcare provider for medical advice is the most impactful step you can take.

If you’re ready to do something about your mental health but not sure what that something is, our mental health services are a great place to start.

In addition to online therapy and online psychiatry, we offer SSRIs like escitalopram (Lexapro®) sertraline (Zoloft®) paroxetine (Paxil®) and citalopram (Celexa®). These might be better fits if you’re seeing significant side effects from Prozac.

Check out our mental health resources to start exploring your options.

4 Sources

Hims & Hers has strict sourcing guidelines to ensure our content is accurate and current. We rely on peer-reviewed studies, academic research institutions, and medical associations. We strive to use primary sources and refrain from using tertiary references.

  1. Jing, E., & Straw-Wilson, K. (2016). Sexual dysfunction in selective serotonin reuptake inhibitors (SSRIs) and potential solutions: A narrative literature review. The mental health clinician, 6(4), 191–196. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6007725/.
  2. HIGHLIGHTS OF PRESCRIBING INFORMATION: PROZAC (fluoxetine hydrochloride) Pulvules for oral use . (n.d.-b). https://www.accessdata.fda.gov/drugsatfda_docs/label/2011/018936s091lbl.pdf.
  3. Rossi, A., Barraco, A., & Donda, P. (2004). Fluoxetine: a review on evidence based medicine. Annals of general hospital psychiatry, 3(1), 2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC356924/.
  4. Sohel AJ, Shutter MC, Molla M. Fluoxetine. [Updated 2022 Jul 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459223/.

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.

Kristin Hall, FNP

Kristin Hall is a board-certified Family Nurse Practitioner with decades of experience in clinical practice and leadership. 

She has an extensive background in Family Medicine as both a front-line healthcare provider and clinical leader through her work as a primary care provider, retail health clinician and as Principal Investigator with the NIH

Certified through the American Nurses Credentialing Center, she brings her expertise in Family Medicine into your home by helping people improve their health and actively participate in their own healthcare. 

Kristin is a St. Louis native and earned her master’s degree in Nursing from St. Louis University, and is also a member of the American Academy of Nurse Practitioners. You can find Kristin on LinkedIn for more information.

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