What are the most common side effects of fluoxetine?
The most common side effects of fluoxetine are listed below. Tell your healthcare provider if you have any of these side effects that bother you.
- Unusual dreams or change in sleep habits
- Sexual problems (see below)
- Loss of appetite, diarrhea, or indigestion
- Nausea, vomiting, or dry mouth
- Feeling unusually weak or tired
- Headache
- Dizziness
- Flu-like symptoms
- Yawning
- Sore throat or sinus infection
- Shaking or tremor
- Sweating
- Feeling nervous or anxious
- Hot flashes
- Rash
Other side effects in children or adolescents include the following.
- Increase in thirst
- Unusual increase in muscle movements or agitation
- Nosebleed
- Peeing more often
- Heavy menstrual periods
- Possible slower growth rate and weight change
There may be other side effects of fluoxetine that are not listed here. Contact your healthcare provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.
What are the serious side effects of fluoxetine?
While less common, the most serious side effects of fluoxetine are described below, along with what to do if they happen.
Suicidal Thoughts or Actions. Fluoxetine or other antidepressants may increase the risk of suicidal thoughts or actions in a small number of children, teenagers, or young adults in the first few months of taking the medicine or when the dose is changed. Depression or other serious mental health conditions are the most important causes of suicidal thoughts or actions. If you or your child is about to harm themselves, call 911 or call or text 988, the Suicide & Crisis Lifeline. Call your healthcare provider right away if you have any of the following symptoms.
- New or increased thoughts of suicide or death
- Suicide attempt
- New or increased feelings of anxiety, depression, or other unusual changes in your mood or behavior
Serotonin Syndrome. Serotonin syndrome is when there is too much of a chemical called serotonin in your body. Fluoxetine can cause serotonin syndrome when it is taken alone or with other medicines that affect serotonin. This condition can be life-threatening. Get emergency help if you have any of the following symptoms of serotonin syndrome.
- Sweating, fever, or flushing
- Confusion
- Feeling agitated or restless
- Seeing or hearing unusual things
- Dizziness
- Fast or racing heartbeat
- Nausea, vomiting, or diarrhea
- Muscle twitching, stiffness, or tremor
- Seizures
Severe Allergic Reactions. Fluoxetine can cause allergic reactions, which can be serious. Stop using fluoxetine and get help right away if you have any of the following symptoms of a serious allergic reaction.
- Breathing problems or wheezing
- Racing heart
- Fever or general ill feeling
- Swollen lymph nodes
- Swelling of the face, lips, mouth, tongue, or throat
- Trouble swallowing or throat tightness
- Itching, skin rash, or pale red bumps on the skin called hives
- Nausea or vomiting
- Dizziness, feeling lightheaded, or fainting
- Stomach cramps
- Joint pain
Extremely Elevated Mood (Mania). People with bipolar disorder have severe high and low moods. The first symptom of bipolar disorder may be depression. People with bipolar disorder who take an antidepressant, such as fluoxetine, may have a higher risk of having mania or a manic episode. Call your doctor right away if you have any of the following symptoms of a manic episode.
- Very increased energy
- Significant trouble sleeping
- Racing, fast-paced thoughts
- Reckless behavior
- Unusually grand ideas
- Excessive happiness or irritability
- Talking faster or more than normal
Seizures. A small number of people who have taken fluoxetine have reported having seizures. There are many different types of seizures and some of them are not easy to recognize. Stop taking fluoxetine and call your healthcare provider if you experience any of the following signs that a seizure is happening or could happen.
- Muscle twitching, jerking, spasms, tremors, or other uncontrolled movements
- Stiffening of your arms and legs
- Feeling anxious, nervous, confused, or a sense of dread
- Feeling dizzy or lightheaded
- Falling or losing consciousness
Abnormal Bleeding. People taking fluoxetine or other antidepressants may have an increased risk of bleeding or bruising. You may be at higher risk if you are also taking aspirin, a nonsteroidal anti-inflammatory drug (NSAID), like ibuprofen or naproxen, or a blood thinner such as warfarin (Coumadin, Jantoven), apixaban (Eliquis), or rivaroxaban (Xarelto). Tell your healthcare provider if you notice any changes in how easily you bruise or bleed.
Glaucoma. In some people, fluoxetine may increase pressure inside the eye and cause or worsen narrow-angle glaucoma, which can lead to blindness. Tell your healthcare provider right away if you have any of the following symptoms of glaucoma.
- Loss of vision
- Eye pain or redness
- Severe headache or vomiting
- Seeing bright, colorful circles around lights (vision halos)
Low Sodium Level. (Hyponatremia). Fluoxetine and other antidepressants may cause low sodium levels, especially in older people or people taking a diuretic (water pill). Severe hyponatremia can lead to death. Call your healthcare provider if you have any of the following symptoms of a low sodium level.
- Headaches
- Weakness or feeling unsteady
- Problems concentrating or thinking, changes in memory, or confusion
Anxiety or Trouble Sleeping. Some people taking fluoxetine may have anxiety, nervousness, or trouble sleeping (insomnia). Talk with your healthcare provider if you have changes to your sleep or you feel more anxious or nervous while taking fluoxetine.
Heart Rhythm Changes. Fluoxetine may cause a rare dangerous heart rhythm problem called QT prolongation and torsade de pointes. Some people have a higher risk of this, including people who are older, have other people in their family who have had these conditions, have low potassium or magnesium levels, or who take some medicines for other heart rhythm problems. Tell your healthcare provider right away if you faint, have shortness of breath, or have changes in your heart rate or rhythm, such as a slow, fast, or skipping heartbeat.
Sexual Problems or Dysfunction. Taking fluoxetine or another selective serotonin reuptake inhibitor (SSRI) may cause sexual problems. Tell your healthcare provider if you have any of the following sexual problems.
- Decreased sex drive
- Delayed ejacul*tion or unable to have an ejacul*tion
- Problems getting or keeping an erection
- Delayed org*sm or unable to have an org*sm
Weight Loss. Some people taking fluoxetine may experience a change in appetite and significant weight loss, especially those who are underweight and are depressed or those who have bulimia. Tell your healthcare provider if you notice any changes in your weight while taking fluoxetine. Children and adolescents should have their weight and height monitored while taking fluoxetine.
