Like all medications, orlistat does carry a risk of side effects. These side effects are usually mild, and most will disappear within a few weeks. However, before taking orlistat it is important to make sure you are aware of the severe side effects and what you need to do if you experience them. This article provides a summary of orlistat side effects, but you should always read the patient information leaflet before taking any medication. 

What is Orlistat?

Orlistat is a prescription medication commonly used to help people lose weight. It works by blocking the digestion of fat, but it is most effective when combined with a healthy diet and exercise. 

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What are the most common Orlistat side effects?

Like all medications, orlistat can cause side effects. The most common side effects affecting more than 10% of people who take orlistat are related to the effects of orlistat on the digestive system. These side effects include abdominal pain, diarrhoea, fatty or oily stools, flatulence, oily anal discharge and an urgent need to open the bowels. In addition to this, headaches are also a common side effect. Some people with type 2 diabetes may also experience low blood sugar levels when taking orlistat. 

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Which side effects do I need to worry about?

Although it is unusual, it is possible to experience an allergic reaction to orlistat. This may produce itching, rash, hives, breathing difficulties, nausea and vomiting. If this happens, you should stop taking orlistat and seek immediate medical attention. 

In rare cases, orlistat can also lead to liver problems. This could cause yellowing of the skin and eyes, itching, dark urine and abdominal pain. If this happens, stop taking orlistat and seek emergency treatment. 

Other rare but severe side effects include skin blistering and bleeding from your anus. Seek immediate medical attention if you experience either of these. 

Diabetic patients should also be aware that orlistat can lead to a reduction in their blood sugar levels, which may need careful monitoring. 

Orlistat may also interact with certain medications. Therefore, speak to your doctor if you are taking anticoagulants, iodine, levothyroxine, amiodarone, HIV medications, immunosuppressants or medications to treat mental health/psychiatric disorders.

Can I take Orlistat if I am pregnant or breastfeeding?

You should not take orlistat during pregnancy as it may cause harm to your baby. In addition, you should avoid orlistat when breastfeeding as we do not know if it may be possible to pass it on to your baby through breastmilk which could have harmful effects. 

Can I drive whilst taking orlistat?

Orlistat does not have any known effect on your ability to drive or use heavy machinery. However, tiredness is a known side effect of orlistat affecting 1-10% of people. if you start to feel tired or unwell as a result of taking orlistat, you should avoid driving until you have recovered. 

What are the less common side effects?

Other less common side effects, affecting 1-10% of people who take orlistat include rectal pain, soft stools, incontinence, bloating, tiredness and changes to your menstrual cycle. 

What should I do if I experience side effects whilst taking Orlistat?

If you are experiencing severe side effects such as an allergic reaction, liver problems (jaundice, itching, dark urine), skin blistering or bleeding, you should stop taking orlistat and seek immediate medical attention. 

Most side effects of orlistat disappear within a few weeks. If you are finding it difficult to cope with orlistat side effects, you should speak to your doctor for further advice. They may be able to help you adapt to the side effects, or offer you an alternative treatment. 

Are there any alternatives to Orlistat?

If you don’t feel orlistat is right for you, there are various other options to try. The first option is to commit to a low-calorie diet and exercise regime. Most weight loss treatments are only effective when combined with a healthy diet and exercise. Local weight loss groups and exercise classes (which may be available on prescription) can help to support you in your weight loss journey. 

If you would like to try a different weight loss medication, injectable treatments can be very effective. Saxenda is a weight loss injection which works by making you feel fuller for longer and reducing your appetite. Wegovy is a new highly-effective weight loss injection which is expected to be available in the UK in 2023. 

If you are severely obese with a BMI of 40 or more, or a BMI of 35-40 with another serious health condition such as diabetes or high blood pressure, you may be eligible for weight loss surgery. Surgery carries a much higher risk than dietary changes or weight loss medications, so is usually only offered to people who have tried medications first. Speak to your doctor if you would like to find out more about weight loss surgery. 

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