The Independent Pharmacy

Orlistat Side Effects - What To Look Out For

Scott McDougall
Scott McDougallMPharmDirector & Registered Manager

Reviewed on 18 Aug 2023

Orlistat is a medicine that is used to aid weight loss and treat obesity. It helps the patient lose weight gradually over time by expelling up to a third of a meal’s fat through the bowels.

While it is an effective weight loss medication, Orlistat can cause a number of side effects and even though almost all medications come with this risk, it is still advisable to know what the potential side effects are and your chances of experiencing them before taking.

On this page, we’ll cover the most common side effects to watch out for, maximum recommended dosage information, possible interactions with medicines and alcohol, and other important information you need to know.

Very common side effects of Orlistat

The most common side effects of Orlistat typically affect around one in 10 people. These include the below, but the most common side effect is headaches:

  • Oily or fatty faeces or oily discharge from your anus — look out for oily spots on your underwear
  • Urgent or increased bowel movements
  • Increased flatulence, sometimes with discharge
  • Headaches
  • Upper respiratory tract infections (RTIs), such as colds
  • Stomach pains or discomfort

All of these effects are temporary and should pass with time. However, if you experience them for a prolonged period of time, or they get worse, consult with your doctor immediately.

Less common side effects of Orlistat

The side effects of Orlistat below are less common than those listed above and include:

  • Softer faeces
  • Faecal incontinence
  • Gum or teeth disorders
  • Bloating — this is more commonly experienced by people with type 2 diabetes
  • Irregular periods
  • Fatigue
  • Lower respiratory tract infections
  • Rectal pain or discomfort

If you do experience any of these side effects for a prolonged period of time or your symptoms start to get worse, speak with your doctor as soon as possible.

Rare side effects of Orlistat

The side effects listed below are rare for users of Orlistat:

  • Cloudy, bloody, or dark urine
  • Contagious diarrhoea
  • Difficulty hearing or earache
  • Increased heartbeat
  • Painful or difficult urination
  • Increased need to urinate
  • Difficulty breathing or swallowing
  • Swelling of the face, feet, or hands
  • Hives or rash
  • Redness on the skin
  • Yellowed skin or eyes
  • Anxiety

If you experience one or more of the above side effects for any amount of time, speak to your doctor immediately.

What is the maximum dosage of Orlistat?

Orlistat is sold in two different doses, 60mg and 120mg, although it is often sold under different brand names.

The recommended maximum dosage for Orlistat is one capsule up to three times daily (if required). Orlistat should be taken immediately before or up to one hour after a meal. It should only be taken with a meal that contains between 1-15 grams of fat.

Orlistat 120mg Capsules
Orlistat 120mg Capsules
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Allergic reactions to Orlistat

Like all medicines, it is possible for some users to experience an allergic reaction as a side effect of taking Orlistat. The symptoms of an allergic reaction to Orlistat include:

  • Hives or a rash
  • Difficulty breathing
  • Swelling in the face, tongue, lips, or throat

If you experience one or more of the symptoms above, seek emergency medical help immediately.

Other side effects of Orlistat that might indicate an allergic reaction include:

  • Severe abdominal pain
  • Bloody urine
  • Painful or difficult urination
  • Liver problems, such as fatigue, dark urine, loss of appetite, or yellowing of the eyes or skin
  • Kidney problems, such as little to no urination, fatigue, or swelling in the ankles or feet

If you experience one or more of these symptoms, speak to your doctor as soon as possible.

Can Orlistat cause diarrhoea?

Some users do experience diarrhoea as a side effect of taking Orlistat. This is due to the way that Orlistat works on the body, expelling dietary fat through the bowels.

However, diarrhoea as a side effect of Orlistat should go away in time if it doesn’t, consult with your doctor.

Can Orlistat cause constipation?

Some users of Orlistat have reported constipation as a side effect of taking the weight loss medication. However, these incidences are so low that there is little data on this. If you experience constipation while taking Orlistat, discuss it with your doctor.

Can Orlistat cause pale stools?

In some cases, Orlistat can cause pale stools as a side effect. Along with dark urine, unusual fatigue, nausea, or unexplained itching, pale stools can be a sign of a liver problem.

If you experience pale stools or any of the above symptoms, consult with your GP straight away.

Is Orlistat effective for weight loss?

Orlistat is proven to be an effective medicine to aid weight loss. Pharmaceutical trials have shown that, when combined with regular exercise, a balanced diet, and healthy habits, Orlistat can help most people lose significant weight while taking the medicine.

You can find out more about what is Orlistat and does it work here, or you can read our customer reviews of Orlistat here.

Orlistat and alcohol

Orlistat does not interact with alcohol, so it is safe to drink alcohol while taking Orlistat. However, alcohol is high in calories. Consequently, drinking alcohol while taking Orlistat might hinder your weight loss journey.

For more advice on how to make Orlistat more effective use our Orlistat diet plan advice.

Can I take Orlistat while breastfeeding or pregnant?

Orlistat does not absorb effectively into the body from the gut. Consequently, it is unlikely that Orlistat can be absorbed into breast milk.

However, there is not enough data to confirm the safety of using Orlistat while breastfeeding. It is therefore not recommended to take Orlistat while pregnant or breastfeeding.

Can I take Orlistat with other medicines?

Orlistat has been known to interact with a number of medications. However, the most significant medications that Orlistat can react with are:

  • Cyclosporine
  • Lomitapide
  • Mipomersen
  • Teriflunomide
  • Leflunomide

Orlistat should not be used in conjunction with other weight loss medicines such as Xenical or Alli.

If you take any of these medicines, consult with your doctor before taking Orlistat. If you are unsure whether Orlistat will interact with any other medicine you are taking, always discuss it with your doctor or pharmacist.

How can I reduce the side effects of Orlistat?

Most side effects of Orlistat are temporary and go away with time. If your side effects do not go away, speak with your doctor as soon as possible.

It is possible to reduce Orlistat’s side effects by measuring how much fat you consume in each meal.

Orlistat works by stopping fats in your food from being absorbed into the gut. It expels any unabsorbed fat through the bowels.

However, Orlistat can only get rid of so much fat per meal. Consequently, if you eat a meal with more than 1-15 grams of fat, you might experience Orlistat’s side effects more frequently.

To reduce the side effects of Orlistat, consume no more than 1-15 grams of fat per meal if you’re taking Orlistat 120 mg capsules.

You can also reduce Orlistat’s side effects by sticking to the correct dosage of Orlistat. Taking more than the recommended dosage of Orlistat after a meal increases its side effects, so stick to the dosage recommended.


Overall, Orlistat’s side effects do not prevent it from being an effective weight loss medication. Any side effects of Orlistat are, on the whole, temporary, and should go away with time.

Orlistat is best used as part of a healthy lifestyle, for instance doing regular exercise, following a balanced diet, and forming healthy habits such as quitting smoking and reducing your consumption of alcohol.

A healthy lifestyle increases Orlistat’s efficiency and aids your weight loss journey so you can reach a healthy, manageable weight.

You can safely buy Orlistat at The Independent Pharmacy. Simply complete the online consultation with one of our UK-compliant doctors and we will confirm whether Orlistat is right for you. Once we have cleared you, we can send your Orlistat with next-day delivery in plain, discreet packaging.


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