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 a mood-enhancing chemical called serotonin in the brain.

When will I feel better?

You may see an improvement in your symptoms after 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 just 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 jump start 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 take in your stride little things that used to worry you.

Fluoxetine won’t change your personality or make you feel euphorically happy. It will simply help you feel like yourself again.

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

How long will I take it for?

Once you’re feeling better it’s likely that you will continue to take fluoxetine for several more months.

Most doctors recommend that you take antidepressants for 6 months to a year after you no longer feel depressed. Stopping before that time can make depression come back.

Is it safe to take it for a long time?

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.

Otherwise there don’t seem to be any lasting harmful effects from taking fluoxetine for many months and years.

How do I come off fluoxetine?

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 – or longer, if you have been taking fluoxetine for a long time.

This is to help prevent any extra side effects you might get as a reaction to coming off the medicine. These include:

  • dizziness
  • 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.

Is fluoxetine better than other antidepressants?

Fluoxetine isn’t any better or worse than other antidepressants.

However, sometimes people respond better to one antidepressant than to another. Talk to your doctor if you aren’t feeling any better after 6 weeks.

Will it affect my contraception?

Fluoxetine does not affect any type of contraception including contraceptive pills or emergency contraception.

Will it affect my fertility?

There’s some evidence that fluoxetine can reduce the quality of sperm – but it’s not known whether this reduces male fertility. The effect should reverse once you stop taking the medicine. Speak to your doctor if you’re concerned.

For women, there’s no firm evidence to suggest that taking fluoxetine will reduce your fertility. However, speak to a pharmacist or your doctor if you’re trying to get pregnant. They may want to review your treatment.

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:

  • men might get painful erections, problems with getting an erection and problems with ejaculating
  • women might have some vaginal bleeding and might not reach orgasm the same way as before
  • you may have 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.

Can I drive or ride a bike?

Some people can’t 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.

Can I drink alcohol with it?

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.

Are there other treatments that will help?

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

  • talking therapy
  • exercise programmes
  • help to get a good night’s sleep

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 recreational drugs affect it?

Cannabis with fluoxetine can give you a fast heartbeat. Cannabis can also make drowsiness worse with fluoxetine, especially in people who have just started taking it.

Methadone can increase the risk of side effects in people taking fluoxetine. It can be potentially 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 hasn’t been properly tested with recreational drugs. Talk to your doctor if you think you might use recreational drugs while taking fluoxetine.