What it is used for

Weight loss in adults with obesity, or who are overweight with a weight-related condition, alongside a lower-fat diet (prescription)
Lower-dose version for overweight adults (from pharmacies)

Read our guides:

Obesity

Off-label uses

Doctors sometimes prescribe a medicine for a condition it is not officially licensed for. This is called off-label use. It is legal and common when there is good evidence it helps, and your doctor should explain why they are suggesting it.

Orlistat is not commonly used off-label.

How it works

Orlistat blocks lipase, an enzyme in the gut that breaks down fat. About a third of the fat you eat is not absorbed and passes out in your poo.

Side effects

Like all medicines, Orlistat can cause side effects, although not everyone gets them. Many are mild and ease after the first few weeks.

Common side effects

oily spotting from your bottom
wind with oily discharge
urgent need to poo
oily or fatty poo
stomach pain

Tell your doctor or pharmacist if these bother you or do not go away.

Serious side effects

These are rare. Call 111 or contact your doctor straight away if you get:

severe stomach pain, or yellowing of the skin or eyes
bleeding from your bottom

Call 999 if you have signs of a serious allergic reaction, such as swelling of your lips, mouth, throat or tongue, or trouble breathing.

You can report any side effect to the Yellow Card scheme, run by the medicines regulator.

Stopping and withdrawal

Important safety information

Side effects are worse after high-fat meals.
Take a multivitamin at bedtime, as orlistat can reduce absorption of some vitamins.
It can make the contraceptive pill less effective if it causes severe diarrhoea.
It may affect levothyroxine, epilepsy medicines and some HIV medicines.

Questions about your medicine?

A pharmacist can answer questions about your medicines for free, without an appointment. You can also ask your GP for a medication review. Check if you can get free prescriptions.