12 Prozac (Fluoxetine) Side Effects You Should Know About

Prozac (fluoxetine) is an antidepressant that’s been around for decades. It belongs to a group of medications called selective serotonin reuptake inhibitors (SSRIs). Prozac is often prescribed for depression. But it can also help with conditions such as obsessive-compulsive disorder (OCD), panic disorder, and bulimia.

Side effects are often a concern when starting Prozac. But they don’t happen to everyone and often improve over time. Knowing what to expect and how to manage Prozac side effects can help you get the most from your treatment.

Prozac (fluoxetine) side effects at a glance

Many Prozac side effects are mild and tend to improve over time. But in rare cases, more serious side effects are also possible. Below are lists of both common and serious Prozac side effects to be aware of. Keep in mind that it’s always a good idea to discuss any side effects you experience with a healthcare professional, even if they aren’t listed below.

1. Insomnia

Insomnia is a common Prozac side effect. That’s because it raises the amount of serotonin in your brain. Serotonin is involved in many processes in the body, including mood regulation and sleep.

Prozac tends to be more energizing than other SSRIs. So, you may have difficulty falling or staying asleep while taking it. Because of this, it’s recommended to take Prozac in the morning.

If you’re having sleeping problems while taking Prozac, let your prescriber know. They may decide to lower your dose, add another medication, or have you try a different antidepressant. They can also provide tips for how to improve your sleep hygiene, such as optimizing your sleep environment.

2. Headache

Headache is a common side effect of SSRIs, including Prozac. For many people, headaches may improve as your body gets used to the medication. But if headaches become bothersome, talk to your healthcare team about over-the-counter options for relief. Acetaminophen (Tylenol) is one example. Keep in mind that nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Motrin, Advil), can interact with Prozac. More on that later.

Good to know: Headache can also be a symptom of low sodium levels in your body (called hyponatremia), which can happen with Prozac. This tends to be more common among older adults and people taking diuretics (water pills). Tell your prescriber if your headaches are accompanied by difficulty concentrating, confusion, or weakness.

3. Drowsiness

Although some people have trouble sleeping while taking Prozac, others may experience drowsiness. It’s a good idea to see how the medication affects you before doing activities that require being alert, such as driving a car.

If Prozac makes you sleepy, this side effect may improve over time. But if drowsiness is interfering with your daily life, talk to your prescriber. While Prozac is usually taken in the morning, they may suggest taking it at night instead.

4. Anxiety and nervousness

In addition to insomnia, anxiety and nervousness are other symptoms of Prozac’s activating effect. These side effects usually happen early in treatment and then improve with time. But for some people, they can be more intense and even lead to panic attacks in some cases.

Although uncommon, these feelings may coincide with more serious issues, such as suicidal thoughts or behaviors (more on that later). So it’s important to tell your prescriber about any changes in your mood or behavior that occur while taking Prozac.

5. Nausea

Nausea is another common Prozac side effect. It tends to happen within the first few weeks of treatment and should improve over time.

You can take Prozac with or without food. But if you’re feeling nauseated after your dose, try taking it with food to see if that helps. Tell your prescriber if nausea doesn’t go away or gets worse. They may decide to lower your dose or switch your antidepressant.

6. Sexual problems

Sexual problems are commonly reported with SSRIs, including Prozac. This can include a lowered sex drive, ejaculation or orgasm problems, and erectile dysfunction. Sexual side effects may improve over time for some people. But this isn’t the case for everyone. It’s also important to note that the cause of sexual problems can be complex. So Prozac may not be the only factor to consider.

Tell your prescriber if you notice any new or worsening sexual problems while taking Prozac. In some cases, they may recommend adding or switching to a medication with fewer sexual side effects, such as bupropion (Wellbutrin XL).

7. Weight gain

Does prozac cause weight gain? Some people taking SSRIs such as Prozac may notice weight gain. But of the SSRIs, Prozac seems to cause the least amount of weight gain. And some people taking Prozac may even lose weight.

Sometimes, weight gain may not be from the medication itself. If you’re gaining weight, review some of your lifestyle habits, such as diet and exercise. Plus, decreased appetite is a common symptom of depression and anxiety. As your symptoms improve, your appetite may improve as well, which could explain any weight gain.

Healthy habits, including a balanced diet and regular exercise, can help you manage your body weight and provide mood-boosting benefits in the process. But if you’re concerned about weight gain while taking Prozac, talk to your prescriber for additional ways to manage it. But don’t stop taking Prozac on your own. Doing so could lead to unpleasant withdrawal effects (more on that later).

8. Sweating

Excess sweating is a common side effect of many antidepressants, including Prozac and other SSRIs. If you find yourself sweating more than usual during treatment, wearing loose-fitting clothing and using an antiperspirant may help.

But if sweating is still a problem, let your prescriber know. They may suggest lowering your dose or switching you to an antidepressant that’s less likely to make you sweat. However, sweating can also be a symptom of serotonin syndrome, which we’ll cover later.

9. Higher risk of bleeding

Prozac and other SSRIs can raise your risk of bleeding, especially in your stomach. This is due to their effects on platelets (cells involved in blood clotting).

The risk of bleeding goes up if you combine Prozac with other medications that raise your bleeding risk. Examples include NSAIDs as well as blood thinners such as warfarin (Coumadin, Jantoven).

Make sure your prescriber and pharmacist have your current medication list. That way, they can review it for potential interactions. And it’s best to double-check with them before adding a new medication or supplement to your regimen. Seek medical care right away if you notice signs of bleeding, such as new or unusual bruising, blood in your stool, or black or tarry stool.

10. Antidepressant discontinuation syndrome

If you abruptly stop taking Prozac or lower your dose too quickly, you may experience antidepressant discontinuation syndrome. Although temporary, this can cause unpleasant symptoms, such as flu-like symptoms, headache, and dizziness.

Compared to other antidepressants, Prozac sticks around in your body for a longer period of time. Because of this, it may have a lower risk of antidepressant discontinuation syndrome. Even so, it’s still important to take Prozac as directed. Avoid discontinuing or lowering your dose on your own.

If you want to stop taking Prozac, talk to your prescriber first. They can help you do it safely to minimize or avoid these symptoms.

11. Serotonin syndrome

Serotonin syndrome is a condition that can happen when there’s too much serotonin in your body. Although uncommon, it’s a possible side effect of Prozac and other SSRIs, since they raise serotonin levels.

Serotonin syndrome may be more likely if you combine Prozac with other medications that raise serotonin levels. Examples include other antidepressants, St. John’s wort, and certain pain medications. Your prescriber or pharmacist can check for these potential interactions.

Signs of serotonin syndrome include sweating, shaking in your hands, and a fast heartbeat. This can progress into confusion, high fever, and uncontrolled movements. In some cases, serotonin syndrome can be life-threatening. Contact your prescriber if symptoms develop. Seek medical care right away if your symptoms feel severe or life-threatening.

12. Suicidal thoughts and behaviors

If you take Prozac to help manage depression, your symptoms may get worse before they get better. Although uncommon, this can include suicidal thoughts and behaviors, especially among people under age 25.

Tell your prescriber right away if you notice changes in your mood or behavior while taking Prozac. These changes may be more likely when starting treatment and after dosage adjustments.

If you or someone you know is having thoughts of suicide, you’re not alone, and help is available. Call the National Suicide Prevention Lifeline at 988, or text HOME to 741-741 to reach the Crisis Text Line.

Prozac (fluoxetine) side effects for women vs. men

Prozac can cause many of the same side effects in women and men, such as headaches and nausea. But when it comes to sexual side effects, men may experience lowered sex drive, ED, and ejaculation problems. Women may experience lowered sex drive and orgasm problems.

There are also reports of menstrual cycle changes among women taking Prozac. This includes heavy or prolonged menstrual bleeding. Talk to your prescriber if you notice that your periods are heavier than usual after starting Prozac.

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Written by:

Sandy P. Bonfin, PharmD, BCPS

Sandy Bonfin, PharmD, BCPS, is a clinical pharmacist at a Florida hospital. Bonfin has worked in pediatric medicine, emergency medicine, internal medicine, and intensive care.

Edited by:

Stacia Woodcock, PharmD

Stacia Woodcock, PharmD, is a pharmacy editor for GoodRx. She earned her Doctor of Pharmacy degree from the University of Kentucky and is licensed in New York and Massachusetts.

Reviewed by:

Ferras Bashqoy, PharmD, BCCCP, BCPPS

Ferras Bashqoy, PharmD, BCCCP, BCPPS, is a clinical pharmacotherapy specialist in the Neonatal Intensive Care Unit at Hassenfeld Children’s Hospital in NYC. He enjoys working with preterm newborns, as they are small but mighty.

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