Fluoxetine, also known by trade names Prozac and Sarafem, among others, is an antidepressant of the selective serotonin reuptake inhibitor class. It is used for the treatment of major depressive disorder, obsessive-compulsive disorder, bulimia nervosa, panic disorder and premenstrual dysphoric disorder.

The recommended dose for adults is:

The usual dose of fluoxetine is 20mg a day in adults. However, you may be started at a lower dose which is gradually increased to a maximum dose of 60mg a day. Some people might need to take a lower dose of fluoxetine, or to take it less often. This includes people with liver problems, and elderly people.

The usual dose of fluoxetine in children is 10mg a day but this may be increased to 20mg a day.

How long will it take to start working?

  • Antidepressants like fluoxetine can start to work on depression within the first two weeks of treatment, and the improvement continues over the following few weeks.
  • For anxiety, antidepressants like fluoxetine can take slightly longer to work. For some people, anxiety briefly increases at the start of treatment, but the anxiety does decrease with continued treatment.
  • See ‘Fluoxetine can help to adjust the chemicals your brain needs’ for the theory as to why it takes time for the benefit of fluoxetine to develop.
  • Some side effects of fluoxetine tend to happen at the start of treatment, but go away after a few days, such as feeling or being sick (nausea or vomiting).
  • To get the best effect, you need to take your fluoxetine every day and give it a chance to work for you.
  • Your doctor might start you on a low dose and then increase it slowly over two to four weeks to your full dose.
  • You and your doctor should talk about how long you need to take fluoxetine.
  • It could take a long time to work for you, but hopefully it will be worth sticking with it.
  • Keep taking fluoxetine as you get better, which can take a few months, and then keep taking the fluoxetine for another 6 to 12 months as advised by your doctor. If your illness has come back, then you should keep taking fluoxetine for at least two years after getting better.
  • This will help keep you well. If you stop taking the fluoxetine too soon, there is more chance that your mental health symptoms will come back.
  • If you get side-effects that you cannot live with, then talk to your doctor about other options.
  • See your doctor if you want to stop fluoxetine to make sure it is not too soon to stop it. Also, the fluoxetine dose may need to be reduced gradually to reduce the chance of side effects when it is stopped.
  • If you have bipolar disorder, it is likely that the doctor will advise for the fluoxetine to be stopped sooner. This is because, in bipolar disorder, there is a risk of your mood becoming too high if an antidepressant is used for too long.

Side Effects:

Very common side effects (could affect more than 1 in 10 people)

  • Difficulty sleeping (insomnia)
  • headache and feeling tired
  • loose poo (diarrhoea)
  • feeling sick (nausea)

Common side effects (could affect up to 1 in 10 people)

  • not feeling hungry  
  • weight loss
  • nervousness, anxiety, restlessness, poor concentration, feeling tense     
  • decreased sex drive or sexual problems, including difficulty staying hard (keeping your erection) in men to have sex
  • sleep problems, unusual dreams, tiredness or sleepiness
  • dizziness
  • change in taste, or dry mouth
  • uncontrollable shaking movements
  • blurred vision
  • heartbeat feels quick and uneven
  • flushing, sweating more, feeling shaky or chills
  • yawning
  • indigestion, being sick
  • rash, itching lumps (hives, urticaria), other skin itching
  • joint pain
  • going to wee more often
  • unexplained vaginal bleeding


If you stop taking fluoxetine suddenly you may get unpleasant withdrawal symptoms. These include:

  • dizziness
  • feeling sick
  • numbness or tingling in the hands or feet
  • trouble sleeping
  • feeling agitated or anxious
  • headaches
  • shaking

Withdrawal symptoms are usually harmless and over within a few days but it’s possible to prevent them by reducing the dose gradually when you stop taking this medicine.

Your Experiences:

If you take or have taken this medication in the past please leave a comment describing your experiences so that we can help the rest of the community understand what to expect and help them decide whether this is the right medication for them. 🙂

8 thoughts on “What is Fluoxetine?

  1. Just to add Prozac like other SSRIs antidepressants can increase one’s risk of suicide especially in younger patients. It’s something not often discussed but SSRIs cause depersonalization and that may add to the risk.

    Liked by 1 person

  2. 75% of the people in my house take Fluoxetine without any obvious side effects. My son is the most recent and the change he underwent was nothing short of astounding. It can be an extremely effective med.

    Liked by 1 person

  3. Both my daughters are on it. My oldest for almost two years and my youngest almost a month now. They both did experience some side effects, increased anxiety for the first two weeks along with outburst, anger and irritability. BUT after the two week mark, I can say it has been a dream! 🙂

    Liked by 1 person

  4. Having a good support network around you for the first two months is essential as it can take a while for the body to adjust. I have PMDD and it took a couple of cycles for me to feel the benefit and the side effects made me feel worse at times

    Liked by 1 person

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