HeadMeds gives young people in the United Kingdom general information about medication. HeadMeds does not give you medical advice. Please talk to your Doctor or anyone else who is supporting you about your own situation because everyone is different. Please read more important details about our site.

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Return to Fluoxetine overview
  1. Use and Action
  2. Warnings and side effects
  3. Sex, drink, weight and everything else
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Taking Fluoxetine to treat eating disorders: Tula's story
I felt better instantly. I can't say if it was partially a placebo effect, with the virtue of finally being diagnosed leaving me feeling consciously much more optimistic

Fluoxetine can be used to treat the following conditions

Headmeds fills the medicines information gaps for young people - things you might want to know about meds like will it affect my sex life? Can I still study? Can I drink?
Headmeds does not give medical advice so this is just general information.
Each medicine has a balance of good and bad effects, and each person gets their own individual effects.
You might want to know just one thing about your medicine, but on each page we have given you the ‘safety headlines’. Please read them as they are important.
We have included lots of information about each medicine - but if you want all the details, please look at the patient information leaflet - which is inside every pack. These leaflets are also at www.medicines.org.uk - where there will be the most up-to-date information.

Safety headlines

  • If you have taken more fluoxetine than it said on the label, you must see a doctor quickly – even if you do not feel any different.
  • Whilst taking fluoxetine some people may think about hurting themselves or committing suicide. You must go straight to hospital with your tablets if you have any of these thoughts.
  • Fluoxetine can also cause rare but serious side effects: allergic reactions (difficulty breathing, swelling of your face or throat, itching skin lumps), rashes or blotches on your skin, and a rare condition called serotonin syndrome (see ‘Warnings and Side Effects’). Go to a hospital if you get any of these symptoms with your medicine.
  • Do not take fluoxetine if you have taken a monoamine oxidase inhibitor antidepressant (MAOI) like moclobemide, phenelzine, isocarboxazid or tranylcypromine in the last 14 days.
  • Stopping fluoxetine suddenly can sometimes cause withdrawal effects, which are usually mild, but for a few people can be severe. Also, if you stop taking fluoxetine too soon, there is more chance that your mental health symptoms will come back. See your doctor if you want to stop fluoxetine or have withdrawal effects after stopping it.
  • You might not be able to concentrate very well, and may feel sleepy, in the first few days after taking fluoxetine – do not drive a car, ride a bike or operate machines until you see how this affects you.
  • If you are pregnant, or thinking of becoming pregnant, please read the pregnancy section (see ‘Sex, drink, weight and everything else’) because fluoxetine may affect the developing baby.

Basic details

Fluoxetine is a type of antidepressant called a Selective Serotonin Re-uptake Inhibitor

A Selective Serotonin Re-uptake Inhibitor (SSRI) helps make more serotonin available in your brain.

Fluoxetine can be used to help with low mood and anxiety

  • It will sometimes be prescribed alongside a ‘talking’ therapy”.

The capsules contain gelatine, the liquid contains a small amount of sugar and alcohol

  • The capsules contain gelatine, which some people do not like to eat because of religious or cultural beliefs.
  • The liquid contains a small amount of sugar (sucrose).
  • The liquid also contains a small amount of alcohol, but it will not affect your blood alcohol levels.

Fluoxetine can be used for a number of conditions

  • Low mood (depression)
  • Eating disorders such as bulimia nervosa and binge eating disorder
  • Obsessive Compulsive Disorder

Fluoxetine can help to adjust the chemicals your brain needs 

  • Serotonin is a naturally occurring chemical messenger (or “neurotransmitter”) that has important roles in areas of the brain that control mood and thinking.
  • Research suggests that depression or low mood is more likely to happen when the brain doesn’t have enough of a chemical called serotonin (also called ‘5HT’).
  • Medicines like fluoxetine are called selective serotonin reuptake inhibitors (SSRIs) because they focus on increasing brain serotonin involved in nerve activity. They work by blocking recycling of released serotonin back in to the nerve endings.
  • This means that the amount of serotonin is increased and the depression and low mood get better.

Fluoxetine is taken once a day

  • You will get the best effect from fluoxetine if you take it regularly every day.
  • Make sure that you know your dose. If it is not written on the label, check it with your pharmacist or doctor.
  • Young people aged 8-18 may start taking fluoxetine at a lower dose using the liquid, and then move on to the capsules if the dose increases.
  • It is usually best to take fluoxetine in the morning. This is to reduce the chance of it causing difficulty sleeping (insomnia). However, it is important to choose a time each day that you can always remember. This could be when you wake up, a mealtime, or when you brush your teeth.
  • It is best taken after food.
  • Swallow the capsule with a drink of water - if you chew it, it tastes bitter.

If you forget to take a dose then just take it as soon as possible, but do not double dose

What to do if you miss a dose:

  • If you remember later during the day, take it as soon as possible.
  • You may find it difficult to sleep if you take it towards bedtime.
  • If you forget to take it by the time of your next dose, just take the next dose.
  • Do not take a double dose.

What might happen?

  • If you forget to take it for a few days, you may start getting withdrawal symptoms and should talk to your doctor about it.

You must go to A&E if you take too much 

What to do if you take too much:

  • If you have taken more fluoxetine than it said on the label, you must get help quickly – even if you do not feel any different.
  • Go to A&E. Take your medicine with you, to show to the doctors. Tell them how much you have taken.
  • Get a friend or family member to go with you, if you can, just in case you feel ill on the way.
  • You might get any of the following signs:
  • feeling sick or being sick
  • having fits
  • an irregular heartbeat or a heart attack
  • breathing difficulties
  • a change in the way you feel, ranging from agitation to falling into a coma.

You are also at risk of getting ‘Serotonin syndrome’. This is when you can get a high fever, agitation, confusion, trembling, shivering and excessive sweating or weird movements of your muscles. This is rare, but you should watch out for it.

It can take 2-3 weeks for fluoxetine to start helping  

  • 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 sick (nausea) or being sick (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.

Most people take fluoxetine for at least 6 months 

  • You and your doctor should talk about how long you need to take fluoxetine.
  • Keep taking fluoxetine as you get better, which can take a few weeks, 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 cope 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 not need to be reduced gradually as it is very long acting and stays in the body for several weeks once you stop taking it.

Reference sources

Search www.medicines.org.uk to find patient information leaflets and prescribing information on fluoxetine. Capsules and liquid are listed separately. The SmPC lists all the inactive ingredients in the product so you can check against any allergies. If you are still unsure about this then speak to your pharmacist.

  • British National Formulary (BNF) and British National Formulary for children. Download the BNF/BNFC app (blue background) on to your mobile device. No longer available for public access via the web 
  • Taylor D, Barnes T, Young A. Maudsley Prescribing Guidelines in Psychiatry, 13th edition. Oxford: John Wiley & Sons, May 2018. ISBN: 978-1-119-44260-8
  • Royal Pharmaceutical Society. Medicines Ethics and Practice (42nd edition). London: RPS, 2018. Standards for pharmacists to work to. It is not a free publication
  • World Anti Doping Agency WADA Prohibited List https://www.wada-ama.org/en/resources/science-medicine/prohibited-list-documents 
  • Choiceandmedication; an independent source of information on many mental health conditions and their medicines with easy to read fact sheets www.choiceandmedication.org Personal subscriptions to download the app available for £1 per month (with proportionate discounts for longer periods) but your local mental health Trust may subscribe and provide information sheets for free.
  • Best Use of Medicines in Pregnancy (BUMPS). Information sheets on drugs in pregnancy http://www.medicinesinpregnancy.org/ 
  • Drugs and Lactation Database (LactMed). Information on drugs in breastfeeding https://toxnet.nlm.nih.gov/newtoxnet/lactmed.htm