Fluoxetine (Prozac): Uses, Dosage & Side Effects

Katelyn Hagerty

Reviewed by Katelyn Hagerty, FNP

Written by Lauren Panoff

Published 07/18/2020

Updated 09/18/2023

In a world where we joke about finding happiness in pill form, Prozac® (and the generic fluoxetine) is one of the most recognizable pharmaceuticals. 

It’s no wonder antidepressant use has steadily increased in recent years. It took enduring a pandemic, awkwardly dancing into a “new normal” and normalizing oversharing on social media to initiate a more open conversation about mental health. 

Thankfully, this extends beyond trendy “self-care” advice to take baths and buy candles. An effort to destigmatize professional mental health support has also surfaced.

Many people feel empowered to finally seek out therapy and treatment — like getting fluoxetine online for depression — and we celebrate that.

But like any other drug, Prozac isn’t for everyone and comes with potential side effects. Fluoxetine should be taken as directed by your healthcare provider, and you should be aware of its advantages and disadvantages before starting treatment. 

Let’s take a deep dive into how fluoxetine works and the factors to weigh if you’re considering this medication.

Prozac is the brand name for fluoxetine. It’s a selective serotonin reuptake inhibitor (SSRI) medication used in the treatment of various mental health disorders, including depression and obsessive-compulsive disorder (OCD).

A standard treatment option for depression and other mental health concerns, this antidepressant medication has found itself in millions of medicine cabinets. 

Fluoxetine was approved by the U.S. Food and Drug Administration (FDA) as a treatment for depression in 1987. As an SSRI, it lifts your mood by increasing the amount of serotonin (aka “the happy chemical”) in your brain.

Fluoxetine Uses

Prozac is approved to treat several mental illnesses. Some healthcare providers might also use it off-label for other conditions associated with depressive episodes.

Fluoxetine may be used for:

  • Anxiety disorders. Overwhelming anxiety or fear that interferes with daily life could be an anxiety disorder. Many people use Prozac for anxiety due to its effectiveness and generally good tolerance. 

  • Panic disorder. This mental health condition involves recurrent, unpredictable panic attacks. Based on their performance in clinical trials, SSRIs are regularly used to help reduce panic symptoms.

  • Bulimia nervosa. Bulimia nervosa is an eating disorder involving periods of overeating, self-induced vomiting and excessive concern about achieving weight loss. Fluoxetine can help improve commitment to treatment.

  • Obsessive-compulsive disorder (OCD). Obsessive-compulsive disorder disorder is characterized by patterns of intrusive thoughts and fears and repetitive behaviors. SSRIs can be effective for treating OCD.

  • Major depressive disorder (MDD). Ongoing depression with feelings of guilt, sleep disturbances and suicidal thoughts could be major depressive disorder. Fluoxetine is often an effective treatment method for this condition with minor side effects.

  • Premenstrual dysphoric disorder (PMDD). A more severe form of premenstrual syndrome (PMS), PMDD causes severe depression, irritability or anxiety. Many providers prescribe Prozac for PMDD for use during the 14 days leading up to menstruation.

Unlike other antidepressants, SSRIs like Prozac increase the amount of serotonin in your brain. They’re called “selective” serotonin reuptake inhibitors because they target serotonin — leaving most other brain chemicals unaffected.

And the mechanism by which SSRIs work is pretty fascinating. 

Picture a crowd of brain cells meandering about at a party in your brain, communicating with one another through chemical messengers called neurotransmitters. One of these neurotransmitters is serotonin, which plays a key role in your mood (as well as sleep, digestion, nausea, blood clotting, sexual functions and bone health). 

When serotonin is passed between brain cells, it’s like handing off the happiness baton. Normally, the sending brain cell will “clean up” the serotonin it passes off by reabsorbing it.

But when you let an SSRI like fluoxetine into the party, it acts like a bouncer, blocking reabsorption from happening. As a result, there’s a growing amount of serotonin on the dance floor.

Still, serotonin plays a complex role in the body. There’s evidence that some people diagnosed with depression have reduced levels of serotonin.

For lots of folks, increasing the amount of serotonin in the brain can help reduce symptoms of depression. Combining SSRIs with other treatment methods, like therapy, is often best.

Starting Prozac can be the first step toward better mental health. But just because fluoxetine helps your brain feel happier doesn’t mean more is better.

Like any medication, it’s important to take fluoxetine as directed by the healthcare professional prescribing it. Note that Prozac has a longer half-life than other SSRIs, so it can take several weeks to feel a difference.

An average starting dosage for Prozac is 20 milligrams (mg) per day, with a max daily dose of 80 milligrams. Higher daily doses may be used in certain cases, depending on the patient’s condition and unique situation.

There are also delayed-release versions that provide up to 90 milligrams of fluoxetine. These are typically taken once a week. Anxiety disorders might start at 20 milligrams per day and increase to up to 60 milligrams a day. 

Your dosage depends on your individual needs. You’ll work closely with your healthcare provider to adjust your prescription as needed until you find your sweet spot.

To get the best out of your prescription and minimize the chances of adverse effects of fluoxetine, always follow your provider’s instructions. Also, it’s generally best to store the medication at room temperature in a dry place away from direct light.

We dig deeper into how much Prozac your provider may prescribe in our Prozac dosage guide.

Missed Dose of Fluoxetine?

If you forget to take your medication, it’s usually best to take it as soon as you remember. But if you’re getting close to when you’d take your next dose, just wait to take it then rather than doubling up on doses. When in doubt, get in touch with your healthcare provider for guidance on what to do about a missed dose of fluoxetine.

Can You Overdose on Prozac?

With the variability in dosages, is it possible to overdose on Prozac? Taking too much Prozac isn’t the same as taking too many painkillers, but it’s still not a good idea. Plus, taking an extra pill won’t give you any added benefits. 

A Prozac overdose could occur if you take more than directed, combine it with certain other medications or supplements or accidentally take too much. 

Serotonin syndrome can happen when your serotonin levels become too high — and it can occur from a fluoxetine overdose.

Serotonin syndrome can cause side effects like

  • Irregular heartbeat or a heart rate of over 100 beats per minute

  • Uncontrollable shivering or tremors

  • Increased blood pressure

  • Sweating

  • Dilated pupils

  • Irregular eye movements

  • Irritability 

  • Elevated body temperature

  • Seizures

  • Coma

To avoid these adverse effects, stick to whatever dosage has been prescribed to you. Never increase or decrease it without first speaking to your healthcare provider.

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Like any drug, Prozac has possible side effects and drug interactions to be aware of.

The most common fluoxetine side effects are often temporary and may pass on their own over several weeks. But others are more serious.

We’ll go over some of the most common side effects of fluoxetine below.

Sexual Health Impacts

One of the most commonly reported sexual side effects of Prozac is reduced sex drive. Women might experience a reduced ability to orgasm, while men may be more likely to struggle with arousal and erectile dysfunction (ED).

Understanding these possibilities can help you and your partner take a proactive approach to prevent deeper intimacy issues.

Mental Side Effects

While intended to help treat depression, fluoxetine may trigger other side effects relating to mental health.

For instance, it’s possible to experience increased anxiety and a worsened mood. Some people have even said taking it caused them to start having weird dreams and trouble sleeping. Dizziness and headaches may also occur.

Digestive Symptoms

Some people report changes in their bathroom habits when taking fluoxetine. This might include diarrhea or indigestion. Additionally, you may notice a sore throat, dry mouth or a loss of appetite.

Weight Changes

Weight loss or gain is possible while on this medication. Antidepressants like fluoxetine, venlafaxine and phenelzine are often blamed for unwanted weight gain, but the evidence is mixed.

When it comes to weight gain and Prozac, it appears to be less likely to promote weight gain than other antidepressants.

Other Physical Symptoms

Fluoxetine may lead to sweating, tremors, weakness, fatigue or skin rash. 

If you notice any strange or worsening symptoms after starting Prozac, don’t hesitate to reach out to your provider. Some physical effects may go away on their own, but it’s best to get medical advice.

If you have an allergic reaction to fluoxetine, trouble breathing, break out in hives or experience any other serious side effects, seek medical attention right away.

FDA Black Box Warning: Suicidal Thoughts and/or Behaviors

Can a pill that’s supposed to help you feel better actually make things worse? Unfortunately, it’s not out of the question that SSRIs like Prozac could lead to deeper depression and feelings of hopelessness. 

The FDA makes this very clear in a black box warning on fluoxetine packaging. Black box warnings were created in the 1970s to notify consumers about serious, permanent or life-threatening side effects of taking certain drugs. In 2004, Prozac received its own black box.

Antidepressants could have a negative effect on anyone. But an increased risk of suicidal thoughts or behaviors has been observed among kids and adolescents — especially during the first few months and with dosage adjustments. 

Fluoxetine Interactions

When starting a new medication like fluoxetine, it’s crucial to be aware of potential drug interactions. This could include prescription medications, over-the-counter drugs or even herbs and dietary supplements. 

We mentioned serotonin syndrome from overdosing on Prozac. The risk of this happening drastically increases when fluoxetine is combined with other substances that also increase serotonin.

Prozac (or fluoxetine) should not be combined with:

  • Other antidepressants, like serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), monoamine oxidase inhibitors (MAOIs) and SSRIs

  • Non-steroidal anti-inflammatory drugs (NSAIDs) used to help reduce pain, fever, and inflammation, such as aspirin, ibuprofen (Motrin® and Advil®) and naproxen sodium (Aleve®)

  • Tryptophan, an essential amino acid that’s converted to serotonin in the body

  • St. John’s wort, an herb thought to have natural antidepressant properties

  • Benzodiazepines, drugs used for seizures, anxiety and alcohol withdrawal that make your brain less active

  • Amphetamines, addictive mood-altering drugs prescribed for adult narcolepsy and sometimes used illegally as stimulants

  • Lithium, a mood stabilizer used to treat bipolar disorder

  • Triptans, a class of drugs used to treat migraines by altering pain signals and circulation to the brain

  • Opioids and other prescription painkillers like fentanyl and tramadol

  • Buspirone, an anti-anxiety medication that works by balancing levels of dopamine and serotonin in the brain

Another potentially hazardous interaction to note is Prozac and alcohol. If you’re used to winding down with a post-dinner glass of wine or enjoying happy hour at your local brewery, there’s nothing wrong with that — unless you’re on fluoxetine. 

As fluoxetine works to increase serotonin in the brain, alcohol has a similar effect on the body. Mixing the two can be a recipe for disaster.

What’s more, alcohol is a downer. Using it with Prozac can increase drowsiness to a dangerous degree. It’s also possible that this combo worsens your ability to make clear decisions.

Tell your healthcare provider about any medications and supplements you’re taking, as well as your drinking habits, before you begin fluoxetine. 

Fluoxetine and Pregnancy

If you’re considering Prozac and pregnancy, know it’s a category C medication, meaning potential risk to a fetus can’t be ruled out.

While not generally recommended, fluoxetine may be prescribed during pregnancy if the potential benefits to the mother are significant enough to be justified.

Babies exposed to fluoxetine during the third trimester may be more likely to have health complications that call for hospital care, breathing support or even tube feeding. Some providers may reduce the amount of Prozac used toward the end of pregnancy if the expecting mother is already on it. 

Other studies have found an association between SSRI use in pregnancy and fetal heart defects — but the risk is small. At the same time, untreated maternal depression can be a safety risk.

What about Prozac and breastfeeding? As with anything a nursing mother consumes, fluoxetine can be transferred through breast milk.

Prozac packaging warns not to use it while breastfeeding, but most reports indicate no major risks. That said, there have been reports of breastfed babies experiencing vomiting, diarrhea, sleep disturbances and irritability associated with maternal fluoxetine use. 

Feelings of low mood and anxiety are common throughout pregnancy and new motherhood. After all, your body and time are largely out of your control, your clothes are uncomfortable, and you spend most of your day trying to translate screams into survival needs. Having a baby isn’t exactly easy.

Some new mothers get their mojo back quickly. But research from the CDC (Centers for Disease Control and Prevention) found that one in eight women experience postpartum depression (also known as PPD or the “baby blues”).

Before you jump on a train heading toward a guilt trip, know that these feelings can coexist with joy — and that’s okay.

The bottom line is that fluoxetine isn’t the top choice for pregnancy or breastfeeding. Still, having an open conversation with your healthcare provider is vital for determining whether taking this medication makes sense for you. 

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Life can knock you down at any moment — and it can be hard to get back up on your own.

It’s okay to need help with your mental health, whether that means online therapy or taking antidepressants like Prozac. Seek the mental health services you need to improve your quality of life.

If you pursue a fluoxetine prescription, remember to:

  • Be patient. Don’t get discouraged by how long it takes Prozac to work — it may take a few weeks to fully kick in. Use this time to be proud of yourself for taking a positive step toward understanding and improving your mental health. Explore other ways to support your mental health, like therapy or hobbies. Practice grace and self-compassion now and always. 

  • Understand the risks. While Prozac is considered a first-line treatment option for depression, that doesn’t mean it’s risk-free. Some people experience side effects, while others may not. Be aware of the many possible drug and supplement interactions, and know it’s not a drug you can use with alcohol. Carefully weigh the pros and cons of fluoxetine and any other medication you may be prescribed.

  • Let your provider in. They’re there to listen, evaluate your needs and offer medical advice to help you make informed decisions. Disclose every prescription, over-the-counter drug and supplement you use. Report any side effects in case an adjustment or medication change is necessary. And never stop or adjust your dosage on your own, as this can lead to side effects, including Prozac withdrawal symptoms.

“Life’s tough, get a helmet” is a famous quote from the ’90s sitcom Boy Meets World, in a scene about dealing with the challenges of life. But having thick skin isn’t always enough to endure the trials we face — and that’s okay.

Seeking virtual therapy or online psychiatry and accepting a prescription for fluoxetine could be the added protection you really need. Explore mental health services and resources from Hers today.

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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.

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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.

Katelyn Hagerty, FNP

Kate Hagerty is a board-certified Family Nurse Practitioner with over a decade of healthcare experience. She has worked in critical care, community health, and as a retail health provider.

She received her undergraduate degree in nursing from the University of Delaware and her master's degree from Thomas Jefferson University. You can find Katelyn on Doximity for more information.

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