Side Effects of Prozac to Be Aware of

Published on: 22 May 2023
Clinically Reviewed by Dr. Muhammad Munir, MD
Prozac side effects

Prozac (Fluoxetine) has become one of the most common psychiatrist prescribed medications for treating symptoms of mental health conditions like depression, obsessive-compulsive disorder (OCD), some eating disorders, and more. Before you take this medication, you should arm yourself with information on the potential side effects of Prozac.

Knowing Prozac side effects will help you make a more informed decision regarding medication use. So, what are the side effects of Prozac? We’re looking at the common, the less frequent but potentially severe, and the long-term implications of taking Prozac over time. We’re also discussing why it’s a good idea to talk to your doctor or healthcare provider about possible Prozac side effects before starting or continuing your treatment. 

Common Side Effects of Prozac

Common side effects of Prozac include nausea, headache, insomnia, drowsiness, dry mouth, and sexual dysfunction. Often, these symptoms disappear after a few weeks as the body adjusts to the medication. However, if side effects persist or worsen over time, you should contact your doctor immediately to receive proper medical advice. 

Prozac week by week side effects typically look like:

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  • Week 1: During the first week of taking Prozac, you may experience common side effects like nausea, headache, insomnia, drowsiness, dry mouth, and increased sweating.
  • Week 2: During week 2 of taking Prozac, some people experience an increase in appetite or weight gain, as well as dizziness or lightheadedness. Other side effects at this stage may include agitation, restlessness, and sexual dysfunction (including decreased libido or difficulty achieving orgasm).
  • Week 3: By week 3 on Prozac, many users report feeling more energetic but also might experience increased anxiety and irritability. This can lead to difficulty concentrating, which can interfere with work productivity and school performance if not managed properly.  

Keep reading to learn what you can expect with each side effect.

1. Nausea

One of the most common side effects of Prozac is nausea, which can range from mild to severe. Prozac also might cause an upset stomach, abdominal pain, and even vomiting. If you experience any of these symptoms while taking Prozac, contact your doctor.

2. Insomnia

Another common side effect is insomnia or difficulty sleeping. This might be caused by increased anxiety or restlessness due to the medication’s effects on serotonin levels in the brain. If sleep issues become a problem, talk to your doctor about adjusting your dosage or trying another antidepressant medication.

3. Headache

Some people who take Prozac experience headaches as their body adjusts to the new medication in their system. Talk to your doctor if you are experiencing frequent headaches while taking Prozac. They can determine if it’s caused by Prozac or something else.

4. Sexual dysfunction

Many antidepressants, including Prozac, have been linked to sexual dysfunction. You might experience decreased libido, erectile dysfunction, delayed ejaculation, and anorgasmia (inability to reach orgasm). If this occurs while taking Prozac, speak with your doctor about other medications that could alleviate these issues without compromising effectiveness.

5. Weight gain/loss

While weight gain isn’t necessarily an obvious side effect of taking Prozac, some users report gaining weight after starting treatment, while others report weight loss. Prozac weight gain or weight loss could be due to changes in appetite caused by the drug.  

“Treatment with Prozac does not typically result in weight gain, although some patients may experience temporary weight loss. Talk to your doctor about any side effects that don’t go away. You might be able to change the dose or try a different treatment.”

Talkspace therapist Bisma Anwar, LMHC

Do Prozac side effects go away?

Oftentimes, some side effects improve within a few weeks. However, sometimes Prozac can cause side effects that don’t go away. If you are wondering how long it takes Prozac to work without side effects, talk to your doctor. Your doctor will help determine if it’s still the right medication for you.

Less Common Side Effects of Prozac

There are some less common side effects of Prozac that you should be aware of, too.  

  • Anxiety: Some people experience increased anxiety when taking Prozac. This may manifest as feelings of restlessness or agitation. If this occurs, talk to your doctor about adjusting your dosage or switching medications.
  • Agitation: Agitation is another possible side effect of Prozac use. It can cause irritability and anger that may interfere with daily activities such as work or school performance. If this happens after you start taking Prozac, let your doctor know so they can help manage symptoms.
  • Dizziness: Dizziness is another potential side effect of taking Prozac, which could lead to difficulty concentrating and performing everyday tasks like driving or operating machinery safely. If you have excessive dizziness, contact your doctor.
  • Dry mouth: Dry mouth is a symptom many people report when they take Prozac; however, it usually goes away after a few weeks once the body adjusts.
  • Tremors: According to research, mild tremors are a possible side effect associated with using Prozac. They can make it difficult to perform tasks like writing neatly or typing.

“Most side effects, like difficulty sleeping, agitation, headache, or stomach upset, are brief and usually go away within the first month of treatment. Prozac is frequently linked to sleeplessness, headaches, agitation, and issues with sexual function. Within a week or two, many of these side effects will go away. However, sexual side effects have been reported in up to 50% of patients and can persist over time.”

Talkspace therapist Bisma Anwar, LMHC

Serious Side Effects of Prozac

Though Prozac is a widely used antidepressant medication, it can have serious side effects. Here are some of the most potentially serious side effects of Prozac you should be aware of:

1. Suicidal thoughts

One of the most concerning side effects associated with Prozac is an increased risk for suicidal thoughts and behavior. This risk is highest among young adults aged 18 – 24, so it’s vital to monitor mental health closely after starting Prozac to aid in preventing this severe side effect.

2. Serotonin syndrome

Serotonin syndrome occurs when too much serotonin builds up due to certain medications that increase levels of the neurotransmitter in your brain. Symptoms include confusion, restlessness, rapid heart rate, sweating, muscle spasms, and shivering. Research suggests that Prozac can cause serotonin syndrome. If left untreated, serotonin syndrome can become life-threatening and requires immediate medical attention.

3. Seizures

Though rare, seizures can occur when taking Prozac, especially at higher doses. If you have a history of seizures, discuss it with your doctor before starting Prozac

4. Allergic reactions

Some people may experience an allergic reaction to Prozac. This adverse reaction can include hives, difficulty breathing, swelling of the face and throat, and/or rash. If you experience an allergic reaction from Prozac, seek medical attention immediately, as these reactions can be life-threatening if not addressed.

Long-Term Side Effects of Prozac

Long-term side effects of Prozac are an important factor to consider if you take an antidepressant. Studies and research show that people who use antidepressants have a 33% higher risk of death and a 14% higher risk of stroke and heart attack. SSRIs (which Prozac is) are also linked to falls in older adults, and some research suggests a link between SSRIs and dementia, although more research is needed. 

Talk to a Doctor About Prozac 

Talk to a doctor or medical professional about Prozac to fully understand any potential side effects. Ask them questions so you can weigh the risks against the benefits.   

Remember that Prozac can have short-term and long-term side effects. While the most common side effects are usually mild, you still want to be aware of them.  

If you want to talk to a psychiatrist about your options, get connected with an online psychiatrist at Talkspace. You can discuss your symptoms, different medication options, and get Prozac online with a prescription. Start improving your mental health today.


  1. Jing E, Straw-Wilson K. Sexual dysfunction in selective serotonin reuptake inhibitors (ssris) and potential solutions: A narrative literature review. Mental Health Clinician. 2016;6(4):191-196. doi:10.9740/mhc.2016.07.191. Accessed February 8, 2023. 
  2. Serrano-Dueñas M. Fluoxetine-induced tremor: Clinical features in 21 patients. Parkinsonism & Related Disorders. 2002;8(5):325-327. doi:10.1016/s1353-8020(01)00043-8. Accessed February 8, 2023. 
  3. Li K, Zhou G, Xiao Y, et al. Risk of suicidal behaviors and antidepressant exposure among children and adolescents: A meta-analysis of observational studies. Frontiers in Psychiatry. 2022;13. doi:10.3389/fpsyt.2022.880496. Accessed February 8, 2023. 
  4. Frank C. Recognition and treatment of serotonin syndrome. Can Fam Physician. 2008;54(7):988-992. . Accessed February 8, 2023. 
  5. Prasher VP. Seizures associated with Fluoxetine therapy. Seizure. 1993;2(4):315-317. doi:10.1016/s1059-1311(05)80148-7. Accessed February 8, 2023. 
  6. Maslej MM, Bolker BM, Russell MJ, et al. The mortality and myocardial effects of antidepressants are moderated by preexisting cardiovascular disease: A meta-analysis. Psychotherapy and Psychosomatics. 2017;86(5):268-282. doi:10.1159/000477940. Accessed February 8, 2023.
  7. Marcum ZA, Perera S, Thorpe JM, et al. Antidepressant use and recurrent falls in community-dwelling older adults. Annals of Pharmacotherapy. 2016;50(7):525-533. doi:10.1177/1060028016644466. Accessed February 8, 2023. 
  8. Moraros J, Nwankwo C, Patten SB, Mousseau DD. The Association of Antidepressant drug usage with cognitive impairment or dementia, including alzheimer disease: A systematic review and meta-analysis. Depression and Anxiety. 2016;34(3):217-226. doi:10.1002/da.22584. Accessed February 8, 2023. 

Talkspace articles are written by experienced mental health-wellness contributors; they are grounded in scientific research and evidence-based practices. Articles are extensively reviewed by our team of clinical experts (therapists and psychiatrists of various specialties) to ensure content is accurate and on par with current industry standards.

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