How it works
What does fluoxetine do?
Fluoxetine is a type of antidepressant called a selective serotonin reuptake inhibitor (SSRI).
Research suggests that depression or low mood is more likely to occur when the brain doesn’t have enough serotonin.
Serotonin (also called '5HT') is a naturally-occurring chemical messenger (or “neurotransmitter”) that has an important role in areas of the brain that control mood and thinking.
Selective serotonin reuptake inhibitors (SSRIs) - like fluoxetine - are thought to work by increasing levels of serotonin in the brain. They do this by blocking the recycling of released serotonin back into the nerve endings.
Fluoxetine is often prescribed alongside a talking therapy.
How long will fluoxetine take to start working?
Antidepressants like fluoxetine can start to work on depression within the first two weeks of treatment, with the improvements continuing over the following 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.
How long will I need to take fluoxetine?
Most people take fluoxetine for at least six to 12 months after they start to feel better.
If you have suffered from depression in the past, you should keep taking this medication for at least two years after you start to feel better.
You and your doctor should talk about how long you need to take fluoxetine before you begin your treatment.
If you stop taking the fluoxetine too soon, the chance that your mental health symptoms will come back increases.
You should take fluoxetine only as agreed with your doctor.
You will get the best effect from fluoxetine if you take it every day at the dose prescribed by your doctor.
Your doctor might start you on a low dose and then increase it to your full dose slowly over two to four weeks.
Make sure that you know your dose. If it's not written on the label, check with your pharmacist or doctor.
Young people aged eight to 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 insomnia (difficulty sleeping). 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.
Fluoxetine is best taken after food.
Swallow the capsule with a drink of water - if you chew it, it tastes bitter.
What if I 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 will happen if I forget to take my fluoxetine?
If you forget to take it for a few days, you may start getting withdrawal symptoms and should talk to your doctor about it.
Stopping the use of fluoxetine
Stopping fluoxetine suddenly can sometimes cause side effects, which are usually mild, but for a few people can be severe. Also, if you stop taking fluoxetine too soon, the chance that your mental health symptoms will come back increases.
Once you start taking an SSRI, the brain adjusts to having a new level of serotonin around. If you stop taking the SSRI suddenly, the balance starts to change again. You could get some symptoms from the change.
Fluoxetine is less likely to cause withdrawal effects upon stopping than other antidepressant medicines. This is because your body takes longer to get rid of it.
You can stop taking fluoxetine safely with your doctor’s help. Many people who take 20mg or less of fluoxetine can stop taking it without problems. For people on higher doses of fluoxetine, the dose may be stepped down over a few weeks to reduce the chance of withdrawal effects.
Fluoxetine and other antidepressants are not addictive. Although there can be withdrawal effects when they are stopped, you will not have cravings for or get ‘hooked’ on an antidepressant.
Some of the withdrawal effects you might get when fluoxetine is stopped include:
- flu-like symptoms such as chills, muscle aches, excessive sweating, headache, and feeling or being sick
- feeling unusually tired or weak
- sleep disturbances such as difficulty sleeping or vivid dreams
- electric shock-like sensations - especially down the spine (back)
- dizziness, especially when moving
- feeling anxious, restless, irritable, or agitated
- difficulty remembering things or concentrating on things
These symptoms should stop after two weeks for most people, but some people can get them for a few months.
The information on this page was reviewed by the College of Mental Health Pharmacy in March 2020.