Fluoxetine: uses, side effects and what to know

Fluoxetine is one of the better known SSRIs. Its NHS page names three main uses: depression, obsessive compulsive disorder and bulimia. Menopause symptoms are mentioned as an occasional use.

Because each of these conditions is managed differently, the amount you are prescribed depends on what is being treated. The NHS does not quote fixed doses, so follow the label from your own prescriber and the leaflet in the box.

Like other SSRIs, fluoxetine increases the level of serotonin, a chemical in the brain linked to mood. The NHS says this may reduce stress and negative thoughts. It treats symptoms and is often combined with talking therapy.

It is made as tablets, capsules or liquid, so a person who cannot swallow capsules has options. Most people take it once a day. A common pattern is to start with a lower dose and increase it after 3 or 4 weeks, so expect your dose to be reviewed rather than fixed on day one.

If you miss a dose, take it as soon as you remember unless the next one is nearly due. In that case skip it. Never double up.

Improvement can take a few weeks, which is a long wait when you feel low. If nothing seems to be changing, tell your prescriber instead of adjusting the dose yourself.

The NHS says most common effects ease after a couple of weeks. Contact a pharmacist or prescriber if they persist.

• Common effects: headaches, nausea, vomiting, diarrhoea or constipation, weight changes, sexual problems, insomnia, dizziness, drowsiness and blurred vision.

• Avoid driving if you feel dizzy, drowsy or have blurred vision.

• Seek urgent help through NHS 111 for serotonin syndrome, thoughts of suicide or self-harm, signs of mania or hypomania, unexplained bruising or bleeding, and signs of an allergic reaction.

The NHS says fluoxetine may be unsuitable for people who have had an allergic reaction to SSRIs, and that diabetes, epilepsy, heart disease, glaucoma, bleeding disorders and a history of mania all need discussion before it is started.

Check any other medicines with a pharmacist. MAOI antidepressants and St John's wort must be avoided, and caution applies to blood thinners and anti-inflammatory painkillers.

In pregnancy the NHS says fluoxetine can be used at the lowest dose that works, and a hospital birth is advised so the baby can be monitored afterwards. Breastfeeding needs a conversation with your doctor because the medicine can pass into breast milk; the NHS mentions sertraline as an alternative that may be considered.

It is best not to drink alcohol, as it can increase drowsiness and other side effects.

Stopping fluoxetine suddenly can lead to withdrawal symptoms. Your prescriber will lower the dose gradually. Side effects can also be reported through the MHRA Yellow Card scheme.