Xenical: prescription drug with 120mg of Orlistat

Xenical is a prescription-only medication that may help you to lose more weight than dieting alone.

In our series of articles on weight loss drugs, we will explore Xenical in more detail to help you decide if it could be the right choice for you.

If you are considering both Xenical and phentermine, please have a look at our detailed comparison article.

What is Xenical?

Xenical is a prescription medication that was approved by the US Food and Drug Administration (FDA) in 1999. Each capsule contains 120mg of orlistat, an ingredient that blocks the absorption of fat to aid weight loss. At the lower dose of 60mg, orlistat has also been approved as an over-the-counter drug under the brand name Alli ( 1 ).

Xenical should only be prescribed for adults and adolescents aged 12 or over. It is indicated for treating those with a body mass index (BMI) of 30 or higher, or 27 or higher if weight-related complications such as high cholesterol or hypertension are also present. In some cases, the drug is prescribed to prevent weight regain after weight loss ( 2 ).

Xenical is manufactured by Roche Pharmaceuticals, headquartered in Basel, Switzerland ( 3 ).

What does Xenical look like?

Xenical is a hard, turquoise capsule. Roche Xenical 120 is imprinted on each capsule in black lettering.

Xenical capsules
Picture of Xenical 120mg capsules

How does it work?

Lipids (a type of fat) are normally broken down by lipase and absorbed into the body from the gut. Lipids are energy-dense and so eating a fatty diet can quickly lead to weight gain. Orlistat is a lipase inhibitor that works by reducing the amount of lipids absorbed from the digestive system.

Of the fat you eat when taking Xenical, around 30% will not be absorbed and instead passes through the digestive system to be excreted in the feces. This leads to a caloric deficit so that even when fat is consumed, weight loss may occur.

However, to maximize weight loss and minimize bowel-related side effects such as greasy stools, it is important to reduce the amount of fat eaten overall ( 4 , 5 ).

How much weight can I lose?

In a study of 80 patients with a BMI of more than 30, patients who took orlistat 120mg three times daily lost significantly more weight than those taking a placebo. In the 24-week study, the average weight loss in the orlistat group was 4.65kg, whereas the placebo group lost around 2.5kg. The group taking orlistat also saw greater reductions in BMI, waist circumference, and cholesterol levels ( 4 ).

In another study that lasted four years, taking 120mg orlistat three times daily was found to reduce the risk of type 2 diabetes occurring in obese subjects. In addition to weight loss, orlistat, therefore, offers other health benefits ( 6 ).

How should I take Xenical?

One Xenical capsule should be taken three times daily within an hour of eating each main meal. If you miss a meal or the meal does not contain fat, the capsule should be omitted. For the greatest weight loss outcome, it is best to take Xenical in conjunction with regular exercise and a hypocaloric diet that contains less than 30% fat.

Many people remain on this treatment for two or more years. A long-term prescription may be considered necessary to prevent weight regain after loss ( 2 ).

Does Xenical have side effects?

Xenical Digestive Effects

Side effects are most likely to occur in the first few weeks or months of taking Xenical, with digestive disorders being commonly described. In most cases, any unwanted bowel symptoms stop within four weeks. Side effects include oily spotting of stool in the underwear, flatus with oily discharge, fecal urgency, passing oily or fatty stools, and urgency or frequency of defecation.

Patients are strongly advised to take a multivitamin tablet when taking Xenical, as the absorption of fat-soluble vitamins is reduced in the presence of orlistat ( 7 ).

What should I avoid when taking Xenical?

Before starting any medication, it is important to be aware of the precautions and potential interactions.


Eating a high-fat diet will not only hinder weight loss but will likely lead to digestive side effects when taking Xenical. It is advised that patients eat a hypocaloric diet with less than 30% of the total calories coming from fat.

Xenical is contraindicated for people who:

  • Are pregnant
  • Have cholestasis (disrupted flow of bile acids)
  • Have chronic malabsorption syndrome
  • Have severe liver or kidney disease
  • Have a known allergy to orlistat or any other ingredient in Xenical.

In rare cases, Xenical has been associated with severe liver injury and changes in kidney function ( 7 ).

Drug interactions

You must make your doctor aware of any prescribed or over-the-counter medications you take. Cyclosporine, levothyroxine, warfarin, antiepileptic drugs, amiodarone, and antiretroviral medications can all interact with Xenical ( 7 ).

Should you try Xenical?

Significant weight loss can be achieved when Xenical is taken with a low-fat, reduced-calorie diet. The digestive side effects can be unpleasant, but they are likely to settle within a few weeks.

If you are committed to eating healthily and taking medication long-term, Xenical could be the right choice for you.

Before making a decision, you may find it helpful to learn more about the other obesity management drugs available on prescription and over the counter. You can also read our in-depth comparison of Xenical vs phentermine.


Where can I buy Xenical?

Xenical is only available on prescription. You will need to obtain a prescription from a licensed medical prescriber before purchasing Xenical from a pharmacy.

Is Xenical an over-the-counter medication?

Xenical capsules contain 120mg of orlistat and are only available on prescription. However, at the lower dose of 60mg, orlistat can be purchased over the counter under the brand name Alli.

Xenical vs. Alli: What’s the difference?

Each prescription Xenical capsule contains 120mg of orlistat, whereas over-the-counter Alli contains just 60mg. Weight loss results tend to be seen more quickly with Xenical as long as the lifestyle changes are adhered to. Xenical may also be more effective in preventing weight regain than Alli ( 8 , 5 ).

How much does Xenical cost?

At Push Health, each capsule is expected to cost around $3. When taking 3 capsules daily, the monthly cost of Xenical would be around $270 ( 9 ).
At Affordable Meds, the cost for 90 generic orlistat 120mg capsules (a one-month supply) costs $150 with shipping ( 10 ).

How fast do you lose weight after starting Xenical?

If you are wondering how long Xenical takes to start working, clinical studies have shown that orlistat leads to greater weight loss than placebo within eight weeks. However, as the active ingredient starts working from the first capsule, you should notice some weight loss within the first week ( 4 ).

How much weight can you lose on Xenical in a month?

The amount of weight you lose will depend on how firmly you can adhere to the low-fat, hypocaloric diet. In clinical studies, patients who took Xenical lost an average of 1.59kg in the first 8 weeks ( 4 ).

When is the best time to take Xenical?

Taking 120mg of orlistat blocks the digestive absorption of around 30% of dietary fat. As the body will continue to absorb 70% of fat, it is important to follow a low-fat diet to improve your chances of successfully losing weight ( 5 ).

How much fat does Xenical block?

Taking 120mg of orlistat blocks the digestive absorption of around 30% of dietary fat. As the body will continue to absorb 70% of fat, it is important to follow a low-fat diet to improve your chances of successfully losing weight ( 5 ).


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2. Rxlist.com Xenical.
3. US Food and Drug Administration Xenical.
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5. ScienceDirect.com Orlistat.
6. Torgerson JS, Hauptman J, Boldrin MN, Sjöström L. XENical in the prevention of diabetes in obese subjects (XENDOS) study: a randomized study of orlistat as an adjunct to lifestyle changes for the prevention of type 2 diabetes in obese patients. Diabetes Care. 2004 Jan;27(1):155-61. doi: 10.2337/diacare.27.1.155. Erratum in: Diabetes Care. 2004 Mar;27(3):856. PMID: 14693982.
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10. AffordableRxMeds.com Orlistat.