What is Fluoxetine and What are the Side Effects?

trusted pharmacist giving information to patient in pharmacy

Fluoxetine is the generic form of Prozac, which was the first drug introduced in a class of medications called selective serotonin reuptake inhibitors (SSRIs). SSRIs like fluoxetine are used to treat mental illnesses like depression and anxiety, among other mental health conditions.  

Share This Post

An estimated 17.3 million American adults, or 7.1 percent of the population, experienced a major depressive episode in 2017, according to the National Institute for Mental Health.

People who suffer from serious depression or major depressive disorder may turn to help from medications like fluoxetine in hopes of relieving their symptoms, in conjunction with talk therapy and lifestyle changes.

Fluoxetine is the generic form of Prozac, one of the most widely recognized depression medications on the market today, but what is fluoxetine and what are the side effects?  

What is Fluoxetine?

Fluoxetine is the generic form of Prozac, which was the first drug introduced in a class of medications called selective serotonin reuptake inhibitors (SSRIs).

SSRIs like fluoxetine are used to treat mental illnesses like depression and anxiety, among other mental health conditions. 

Fluoxetine was approved by the U.S. Food and Drug Administration (FDA) under the brand name Prozac in 1986, and it’s status as the first medication in a new class of antidepressants has since made it a household name.

Nearly 22 million prescriptions were written for fluoxetine in 2017, making it one of the most popular SSRIs on the market.

What is Fluoxetine Used to Treat?

After its approval for the treatment of clinical depression in 1986, fluoxetine has since been approved for the treatment of many other mental health conditions, including major depressive disorder (MDD), panic disorder, bulimia nervosa, obsessive compulsive disorder (OCD), and premenstrual dysphoric disorder (PMDD).

A brief explanation of each of these conditions and their associated symptoms is provided below.

Clinical Depression/Major Depressive Disorder

When most people think of depression, they are picturing the symptoms of clinical depression, also known as major depressive disorder.

Clinical depression is caused by persistent and intense feelings of sadness that continue for long periods of time. In addition to impacting your mood and behavior, depression can cause physical symptoms that impact your sleep habits and appetite. 

People with major depressive disorder often have trouble performing daily activities and tasks, lose interest in doing things they once enjoyed, and may exhibit suicidal thoughts or behaviors.

An episode of depression impacts an estimated seven percent of American adults each year. 

Symptoms of major depressive disorder include:

  • Lost of interest in activities you used to enjoy
  • Difficult concentrating and low energy
  • Feeling sad, empty, or tearful
  • Feelings of worthlessness, guilt, hopelessness, or helplessness
  • Feelings of moving or thinking in slow motion
  • Suicidal thoughts or behaviors
  • Sleeping and eating more or less than usual
  • Nervous energy
YouTube player

Obsessive Compulsive Disorder

Obsessive compulsive disorder, or OCD, is a mental illness that is characterized by obsessive, worrisome thoughts that cause anxiety.

People with OCD perform compulsive behaviors in order to relieve the anxious thoughts, which may center around  the loss of a loved one.

Compulsions associated with OCD manifest themselves in different ways for each person, but one notable constant is that people with the condition feel compelled to perform the behaviors even when they do not want to or it is inconvenient.

Obsessive compulsive disorder is often first diagnosed in childhood or early adulthood and intensifies later in life. Symptoms include:

  • Need for symmetry and order, including obsessive cleanliness
  • Feeling that you can protect other people by performing certain behaviors or rituals
  • Anxiety about germs and dirt
  • Fear of contamination
  • Difficulty throwing away things of little to no value (hoarding tendencies)
  • Disturbing thoughts 

People with obsessive compulsive disorder may experience some of the following symptoms:

  • Hoarding unnecessary possessions of little value
  • Rearranging things continuously to get them “just right”
  • Excessive hand washing, showering, or repetitive cleaning
  • Checking things over and over again, such as making sure the door is locked

Panic Disorder

Panic disorder is a type of anxiety disorder in which a person suffers from unexpected and repeated episodes of intense fear that results in physical symptoms.

Panic disorder causes physical symptoms that when combined are called panic attacks; symptoms include shortness of breath, heart palpitations, chest pain, sweating, dizziness, and nausea.

Bulimia Nervosa

Bulimia nervosa is an eating disorder that is characterized by binging and purging (eating an unusually large amount of food, often in a short amount of time, past the point of fullness and then purging the food to prevent weight gain).

Common purging methods include laxative abuse, induced vomiting, or excessive exercise.

Premenstrual Dysphoric Disorder

Premenstrual dysphoric disorder (PMDD) is a mental illness that features extreme experiences of depression, tension, and irritability prior to menstruation.

While many women experience mild forms of these symptoms before menstruation, women with PMDD experience extreme forms. 

What are the Benefits of Using Fluoxetine?

Fluoxetine is the first SSRI introduced to the market, and since its invention, many new SSRIs have been added.

However, the medication offers many benefits and remains one of the most popular SSRIs on the market despite the competition. Benefits associated with the use of Fluoxetine include:

  • The medication is shown to be effective at treating a wide range of mental health conditions, including panic disorder, bulimia nervosa, major depressive disorder, obsessive compulsive disorder, and premenstrual dysphoric disorder. Individuals who have been diagnosed with more than one of these conditions may be able to receive treatment with just one medication.  
  • People with naturally low energy levels or those who are experiencing low energy as a result of their depression may find that fluoxetine increases their energy levels.
  • People who have their energy levels increased when taking fluoxetine may experience easier weight loss, which is helpful for those who are overweight. 
  • Fluoxetine is better tolerated by older adults than other SSRIs because it does not carry the risk of adverse effects associated with the heart.
  • Children with major depressive disorder or obsessive compulsive disorder can be treated safely with fluoxetine.

How Do I Know What Dose of Fluoxetine to Take?

The right dose of fluoxetine  will be determined by your health care professional based on your age and the purpose of treatment.

Many people taking fluoxetine and other SSRIs need to have their dosage adjusted several times before finding the appropriate dose

Adults suffering from major depressive disorder generally take 20 mg of fluoxetine each morning to begin treatment.

Doctors may increase your dose by 20 mg every few weeks as needed, but most people take between 20 and 60 mg per day. It is not recommended to exceed 80 mg per day of fluoxetine.

Some people prefer to take the delayed release version of fluoxetine, which is taken weekly. When taking the delayed release oral capsule, patients will take one 90 mg capsule per week.

The effects of Fluoxetine are normally experienced in about four weeks.

Fluoxetine can cause withdrawal symptoms if  the dose is changed or the medication is stopped abruptly, especially if the patient has been taking the medication for six weeks or more, so it is important that patients do not stop taking fluoxetine or change their dose without receiving guidance to do so from their healthcare provider.

Symptoms of withdrawal include:

  • Nightmares and insomnia
  • Vertigo
  • Nausea
  • Aggression
  • Dizziness
  • Confusion
  • Flu-like symptoms
  • Anxiety
  • Tremors
  • Gastrointestinal issues (diarrhea, nausea)
  • Agitation
  • Irritability

What are the Side Effects of Fluoxetine?

Possible Side effects associated with Fluoxetine generally fall into two categories: common and rare/serious.

Common side effects associated with Fluoxetine include:

  • Diarrhea
  • Dry Mouth
  • Increased sweating
  • Headache
  • Nausea
  • Sexual dysfunction, such as difficulty with orgasm or ejaculatory delay
  • Fatigue
  • Drowsiness
  • Feeling nervous
  • Restlessness
  • Difficulty sleeping (insomnia)
  • Decreased libido (sex drive)
  • Loss of appetite

Rare but serious side effects associated with fluoxetine include:

  • Low sodium blood levels, as evidenced by:
    • Difficulty concentrating
    • Headache
    • Weakness
    • Difficulty remembering
  • Angle closure glaucoma, as evidenced by:
    • Swelling or redness in or around eye
    • Eye pain
    • Changes in vision
  • Risk of serotonin syndrome, as evidenced by:
    • Confusion
    • Severe muscular tightness
    • Shivering
    • Diarrhea
    • Fever
    • Seizures
  • QT prolongation and ventricular arrhythmia including changes in the electrical activity of your heart
  • Teeth grinding

If you experience allergic reactions such as hives or difficulty breathing, seek medical advice immediately.

Who Should Not Take Fluoxetine?

People who take certain types of medications known to cause dangerous drug interactions with fluoxetine, including drugs metabolized by CYP2D6, tramadol, fentanyl, St. John’s Wort, tricyclic antidepressants (TCAs), monoamine oxidase inhibitors (MAOIs), especially methylene blue, phenelzine, pimozide, isocarboxazid, and thioridazine, benzodiazepines, antipsychotic drugs, anxiolytic drugs, or other SSRIs/SNRIs including but not limited to olanzapine, citalopram, sertraline, tranylcypromine, venlafaxine, amitriptyline, buspirone, diazepam, NSAIDs including ibuprofen, and blood thinners should not take fluoxetine. Make sure to always check with your doctor before taking any new medications.

People who are allergic to fluoxetine should not take the medication.

Some other groups of people should also use caution when taking fluoxetine. Be sure to give your doctor a complete medical history, especially including any personal or family history examples of:

  • Liver problems
  • Diabetes
  • Bipolar disorder or manic-depressive disorder
  • Personal or family history of suicide attempts
  • Seizures
  • Stomach/intestinal ulcers
  • Low sodium in the blood
  • Severe loss of body water/dehydration
  • Glaucoma (angle-closure type)

Older adults may be at an increased risk of side effects when taking fluoxetine, especially bleeding and loss of coordination. The increased risk of loss of coordination corresponds to an increased risk of falling, which can be serious and even fatal for the elderly. Older adults are also at increased risk of developing low blood sodium.

References, Studies and Sources:





We are committed to providing our readers with only trusted resources and science-based studies with regards to medication and health information. 

Disclaimer: This general information is not intended to diagnose any medical condition or to replace your healthcare professional. If you suspect medical problems or need medical help or advice, please talk with your healthcare professional.

Share This Post

Pharmacists.org Discount Club

Get Started for $1.

  • Cheapest cash pay option at your retail pharmacy
  • 1,000s of drugs below $10.00 that can beat your co-pay
  • Start for $1 for your first month. Cancel anytime. 
  • Tell us your meds, we tell you the cheapest options.

Popular Destinations

Recent Articles

trusted pharmacists giving patient information

Does Taking Effexor Cause Weight Gain?

Taking Effexor may cause weight gain in some patients. Weight gain is a common side effect of Effexor and other antidepressant medications, and more than half of patients on newer classes of antidepressants report experiencing weight gain.

Read More »

Cerebral Review: Online Depression & Anxiety Treatment

Today, we’re deep diving with a Cerebral review to give you some insider info to help you narrow down your choices.

We review and include products we think are useful for our community. If you buy through links on this page, we may earn a commission. For more info, please read our ad policy, content principles and vetting policy.

Read More »

Share On:

More To Explore

Does Taking Effexor Cause Weight Gain?

Taking Effexor may cause weight gain in some patients. Weight gain is a common side effect of Effexor and other antidepressant medications, and more

How Long Does Lexapro Take To Work?

If you are considering taking Lexapro for your depression or anxiety, you might be wondering how long it takes to work.

Zoloft and Weight Loss: Everything You Need To Know

When it comes to Zoloft and weight loss, here’s everything you need to know.

Cerebral Review: Online Depression & Anxiety Treatment

Today, we’re deep diving with a Cerebral review to give you some insider info to help you narrow down your choices.

We review and include

What are the signs of Depression?

In this article, we will discuss the signs and symptoms of depression as well as some treatment options for this condition.

Can You Use Gabapentin For Anxiety?

While Neurontin is the most common brand name for gabapentin, other forms (such as Horizant and Gralise) may be prescribed depending on the specific

What is Zoloft?

If you have been recently diagnosed with depression and are given Zoloft, you may want to know how the medication works, what common side

What is Venlafaxine HCL ER?

The prescription drug belongs to a class of drugs called selective serotonin norepinephrine reuptake inhibitor antidepressants (SNRIs), which are commonly used to treat mental

Using Prozac With Alcohol: What Are the Risks?

Prozac can be used to treat many different mental health conditions, is associated with a relatively low risk of side effects, and causes the

How Long Does Clonazepam Stay in Your System?

This fast-acting medication is known for being effective at panic attacks, but how long does clonazepam stay in your system?

What is Sertraline and What are the Side Effects?

Sertraline is the generic form of Zoloft, a medication that belongs to a class of drugs called selective serotonin reuptake inhibitors (SSRIs). SSRIs like

Turn On, Tune In, and…. Heal Your Brain? Psychedelics Return as Potential Therapy for Mental Health Disorders

Before they fell out of favor over half a century ago, psychedelic drugs, like psilocybin and LSD, were studied for various psychiatric diseases such

How Long Does Alprazolam Stay in Your System?

Alprazolam is a fast-acting medication, but exactly how long alprazolam stays in your body varies tremendously based on the form of the medication taken,

Paxil vs Zoloft: Differences, Similarities and Which is Better

When it comes to Paxil vs. Zoloft, which is better?

A Supplement for Stress? The Science Behind Adaptogens

Stress is part of all our lives. Adaptogens are a group of herbal supplements studied throughout history as a way to improve the body’s

Does Buspirone Cause Weight Gain?

Many antidepressants can cause weight gain as a side effect. Buspirone may cause an altered appetite as a side effect, which can lead to

Duloxetine Withdrawal: Symptoms, Timeline, and Treatment

Duloxetine withdrawal is very common and well documented, affecting nearly half of all patients. Common withdrawal symptoms include dizziness, headaches, and nausea, and symptoms

Cymbalta vs. Prozac: Comparison Guide

Cymbalta and Prozac are commonly prescribed medications to treat mental health conditions such as major depressive disorder. The medications are similarly effective, although one

How Long Does Ativan Stay in Your System?

If you use Ativan to manage your health but are curious about how long Ativan lasts in your system, we have all the information

Why is Mental Health Important?

As the saying goes, “There is no health without mental health,” but why is mental health so important? The reality is that although we

What is BuSpar? Uses, Costs, Benefits, and Doses

If you’re one of 40 million American adults suffering from an anxiety disorder or experiencing symptoms of anxiety, you might think that your battle

What are Long-Acting Injectable Antipsychotics? 

Long-acting injectable (LAI) antipsychotics have been shown to prevent psychosis relapse in patients with schizophrenia. To combat poor medication adherence, LAIs are a great

Cymbalta vs Effexor: Differences and Side Effects

Effexor and Cymbalta are antidepressants used for the treatment of major depressive disorder and generalized anxiety disorder. Although both medications are FDA-approved, Effexor and

Celexa vs Lexapro: Which is Better For Depression?

Both are regarded as equally effective drugs for treating depression. Find out the core difference between Celexa vs. Lexpro now!

What is Ativan? Uses, Costs, Benefits, Doses

More than 40 million adults in the United States are diagnosed with an anxiety disorder, making it the most common mental illness in the

Lexapro Overdose: Signs, Symptoms, and Precautions

We’ve put together a list of the signs and symptoms to look out for when it comes to Lexapro overdose and some of the

Panic Attacks: The Story of an Overpowering Fear

Panic attacks are when you experience a sudden feeling of intense fear with no apparent threat or danger.  This triggers a "fight or flight"

Using Lorazepam with Alcohol: What Are the Risks?

Using lorazepam with alcohol is incredibly dangerous but can be a common occurrence, and is associated with potentially life-threatening side effects, which are outlined

Using Citalopram with Alcohol: What Are the Risks?

Mixing antidepressants with alcohol is always potentially dangerous, but using citalopram with alcohol is particularly unsafe due to the high potential for life-threatening side

Brightside Health Review: Is This Depression & Anxiety Care Useful?

Brightside is an online mental healthcare company that provides treatment services for a range of issues related to anxiety and depression. These conditions include