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Common questions about fluoxetine

How does fluoxetine work?

Fluoxetine is one of a group of antidepressants called selective serotonin reuptake inhibitors, or SSRIs. These medicines are thought to work by increasing the levels of serotonin in the brain. Serotonin is thought to have a good influence on mood, emotion and sleep.

When will I feel better?

You may see an improvement in your symptoms after around 1 to 2 weeks, although it usually takes between 4 and 6 weeks before you feel the full benefits. That's because it takes around a week for fluoxetine levels to build up in your body, and then a few weeks longer for your body to adapt and get used to it.

Do not stop taking fluoxetine after 1 to 2 weeks jus because you feel it is not helping your symptoms. Give the medicine at least 6 weeks to work.

How will it make me feel?

Antidepressants like fluoxetine help to improve your mood so you feel better.

You may notice that you sleep better and get on with people more easily because you're less anxious. You will hopefully feel less worried.

Fluoxetine will not change your personality, it will simply help you feel like yourself again.

Do not expect to feel better overnight, though. Some people feel worse during the first few weeks of treatment before they begin to feel better.

Are there any long-term side effects?

For most people, fluoxetine is safe to take for a long time.

A few people may get sexual side effects, such as problems getting an erection or a lower sex drive. In some cases, these can continue even after stopping the medicine. Speak to your doctor if you are worried.

There do not seem to be any lasting harmful effects from taking fluoxetine for many months and years.

What will happen if I stop taking it?

If you’ve been feeling better for 6 months or more, your doctor may suggest coming off fluoxetine.

Your doctor will probably recommend reducing your dose gradually over several weeks if you have been taking fluoxetine for a long time.

This helps to prevent any withdrawal symptoms. This sometimes happens as a reaction to coming off the medicine. These include:

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


Do not stop taking fluoxetine suddenly, or without talking to your doctor first.

How does fluoxetine compare with other antidepressants?

Fluoxetine is no better or worse than other antidepressants. However, sometimes people respond better to one antidepressant than to another. Talk to your doctor if you are not feeling any better after 6 weeks.

Are there other treatments for depression that will help?

Antidepressants, including fluoxetine, are just one of several approaches to treating depression. Other potential treatments include:

Choosing a treatment that's most suitable for you depends on:

  • how long you've had depression
  • your symptoms
  • whether you've had any previous periods of depression
  • whether previous treatment has worked
  • how likely you are to stick with your treatment
  • the potential side effects
  • your preferences and priorities
Will it affect my sex life?

The good effects of fluoxetine may, after a while, improve your sex life as your mood lifts and you become interested in life and relationships again.

Some of the possible negative effects include:

  • painful erections, problems with getting an erection and ejaculating
  • some vaginal bleeding and not reaching orgasm the same way as before
  • having a lower sex drive

Sexual side effects usually pass after the first couple of weeks. However, very rarely, they can be long lasting and may not get better even after stopping the medicine.

If these happen and are a problem for you, go back to your doctor to see if there's another treatment you can try.

Will I gain or lose weight?

Fluoxetine can make you feel less hungry than usual, so you may lose weight when you start taking it.

If you start to have problems with your weight while taking fluoxetine, talk to your doctor or pharmacist.

Will it affect my contraception?

Fluoxetine does not affect any type of contraception including the combined pill or emergency contraception.

But if you have severe diarrhoea for more than 24 hours, your contraceptive pills may not protect you from pregnancy. Check the pill packet to find out what to do.

Read what to do if you're on the pill and you have diarrhoea.

Can I drive or ride a bike?

Some people cannot concentrate properly while they're taking fluoxetine. It might be best to stop driving and cycling for the first few days of treatment until you know how this medicine makes you feel.

It's an offence to drive a car if your ability to drive safely is affected. It's your responsibility to decide if it's safe to drive. If you're in any doubt, do not drive.

Talk to your doctor or pharmacist if you're unsure whether it's safe for you to drive while taking fluoxetine. GOV.UK has more information on the law on drugs and driving.

Can I drink alcohol while taking fluoxetine?

You can drink alcohol while taking fluoxetine but it may make you feel sleepy. It might be best to stop drinking alcohol for the first few days of treatment until you see how the medicine affects you.

Is there any food or drink I need to avoid?

You can eat and drink normally while taking fluoxetine.

Will recreational drugs affect it?

Using cannabis while you’re taking fluoxetine can give you a fast heartbeat. If it makes you feel drowsy, cannabis can also make this worse.

Methadone can increase the risk of side effects in people taking fluoxetine.

It can also be dangerous to take fluoxetine with:

  • stimulants like ecstasy (MDMA) or cocaine
  • hallucinogens like LSD
  • novel psychoactive substances (which used to be known as legal highs) like mephedrone

Fluoxetine has not been properly tested with recreational drugs. Talk to your doctor if you think you might use recreational drugs while taking fluoxetine.

Find out more about some of the side effects of recreational drugs on the Frank website.

Page last reviewed: 10 February 2022
Next review due: 10 February 2025