Orlistat - Common brands: Alli, Orlos, Xenical

What orlistat is for

Orlistat treats obesity by helping you lose weight when you combine it with exercise and changes to your diet.

It works by reducing how much fat is absorbed into your body. A third of the fat from your food is passed out in your poo.

You’ll only be prescribed orlistat if you have either:

• a body mass index (BMI) of 28 or more and a weight-related condition, such as type 2 diabetes or high blood pressure (hypertension)
• a BMI of 30 or more

If you're not eligible for NHS treatment, you may be able to buy orlistat privately.

If you decide to get a private prescription for orlistat, it's important to buy it from a registered pharmacy. There are some websites that sell fake weight loss medicines.

How to take orlistat

Orlistat comes as capsules that you take 3 times a day with a meal. Swallow the capsules with water.

Always check the packet or leaflet that comes with your medicine. Ask a pharmacist or doctor for advice if you're not sure how to take it or you have any problems using it.

You need to take orlistat:

• before a meal
• with a meal
• up to 1 hour after a meal

You can choose the option that suits you best, but try to take your medicine the same way every mealtime.

If you miss a meal, or your meal does not have fat in it, do not take a capsule.

If you miss a dose of orlistat

If you forget to take a dose of orlistat and:

• it's 1 hour or less since your last meal, take the missed capsule
• it's more than 1 hour since your last meal, do not take the missed capsule

Then take the next capsule with your next meal as usual.

Do not take 2 doses at the same time to make up for a missed one.

If you take too much orlistat

Taking an extra dose of orlistat is unlikely to cause problems, but it's important to get medical advice if you take too much because it could be dangerous.

How to stop taking orlistat

Taking orlistat for more than 3 months is not recommended if you have not lost 5% of your body weight. Your doctor may advise you stop treatment and talk to you about other options.

It's important to carry on eating a balanced diet and to exercise regularly after you stop taking orlistat to help you maintain a healthy weight.

Side effects of orlistat

Like all medicines, orlistat can cause side effects, but not everyone gets them.

Common side effects

Common side effects of orlistat include:

• fatty or oily poo
• needing to poo urgently or more frequently
• farting with or without oily spotting
• stomach pain
• diarrhoea

You're less likely to get these side effects if you stick to a balanced diet and avoid meals that are very high in fat.

Serious side effects

Orlistat can sometimes cause serious side effects, but most of them are rare.

Possible serious side effects of orlistat include:

• an allergic reaction (anaphylaxis), which can cause symptoms such as a swollen throat or tongue, a raised, itchy rash or difficulty breathing
• inflamed pancreas (acute pancreatitis), which can cause severe pain in your tummy or back that does not go away
• bleeding from your bottom (rectum)

Who can and cannot take orlistat

Most adults can take orlistat.

Orlistat is not suitable for some people. For example, it may not be suitable if:

• you've had an allergic reaction or serious side effect from orlistat
• you have a liver condition called cholestasis
• you have chronic kidney disease (CKD), or a condition that can stop vitamins and minerals being absorbed into your body

Before taking orlistat, tell your doctor or a pharmacist if you have any medical conditions.

Breastfeeding and orlistat

Tell your doctor if you're breastfeeding.

Orlistat is not usually used while breastfeeding as it's not known if the medicine passes into breast milk.

Pregnancy and orlistat

Tell your doctor if you're pregnant or become pregnant while using orlistat.

Orlistat is not used during pregnancy as there's not enough information to say it's safe for your baby.

Taking orlistat with other medicines, food and drink

There are some medicines, herbal remedies and supplements that may not mix well with orlistat.

These include:

• some medicines to prevent blood clots, such as warfarin
• amiodarone, a medicine for heart rhythm problems
• HIV medicines
• medicines for depression or anxiety
• levothyroxine, for an underactive thyroid (hypothyroidism)

Before you take orlistat, tell your doctor or a pharmacist if you're taking any other medicines, herbal remedies, vitamins or supplements.

If you bought orlistat without a prescription, check the packet or leaflet that comes with the medicine to see if it's suitable for you. Speak to a pharmacist or doctor if you're not sure if you can take it.

Orlistat and contraception

If you're taking orlistat and the combined pill and you have severe diarrhoea, or diarrhoea that lasts for more than 24 hours, your contraception may not protect you from pregnancy. Use an additional barrier contraception, such as condoms, a diaphragm or cap.

Food, drink and alcohol with orlistat

You'll need to eat a healthy, calorie-controlled diet while taking orlistat, with plenty of fruit and vegetables.

You'll also need to eat some fat when taking orlistat, but avoid high fat foods like processed or fatty meats, fried food, biscuits and cakes.

Find out more about eating a healthy, balanced diet