Orlistat for Weight Loss: Side Effects & Where to Buy

What Is Orlistat?

Trying to lose weight can sometimes feel like an uphill battle. And when diet and exercise alone don’t work, you may start to research medication options. Orlistat is an FDA-approved weight-loss medication that targets how your body handles dietary fats.

Classified as a lipase inhibitor, orlistat works directly in your digestive system to block fat absorption. The medication is available in two forms, prescription-strength Xenical® (120 mg) and over-the-counter Alli® (60 mg).

However, orlistat isn’t a standalone solution. It’s intended for use alongside a reduced-calorie diet and regular physical activity to support weight loss.

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How Does Orlistat Work for Weight Loss?

When you eat foods containing fat, your body releases enzymes called lipases in the stomach and pancreas. These enzymes break dietary fats (triglycerides) into smaller components—free fatty acids and monoglycerides—that can be absorbed into the bloodstream.

Orlistat works by inhibiting these lipase enzymes. When lipase activity is blocked, about 30% of the fat you consume isn’t broken down or absorbed. Instead, it passes through the digestive system and is eliminated via bowel movements.

Because fat contains nine calories per gram, reducing fat absorption lowers overall calorie intake, which can support weight loss over time. Clinical studies have shown that people who used orlistat alongside a reduced-calorie diet lost more weight over one year than those who relied on lifestyle changes alone.

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Who is a Good Candidate for Orlistat?

To qualify for prescription orlistat, you typically need a body mass index (BMI) of 30 or higher, which falls under the clinical definition of obesity. Those with a BMI between 27 and 29.9 may also be candidates if they have weight-related health conditions such as high blood pressure, type 2 diabetes, or high cholesterol.

Additionally, Xenical® is approved for adults and adolescents 12 years and older, while over-the-counter Alli® is available only to adults 18 and older.

However, you should avoid this medication if you have chronic malabsorption syndrome, cholestasis (reduced bile flow), active gallbladder problems, a history of pancreatitis, or a history of oxalate-type kidney stones. Pregnant or nursing mothers should also not take orlistat.

If you take cyclosporine, you’ll need to space your doses at least two hours apart from orlistat. Always consult a healthcare provider before starting this medication, especially if you have pre-existing conditions or take other medications.

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Orlistat Side Effects

Like all medications, orlistat may cause side effects. 

The most frequently reported orlistat side effects are gastrointestinal. These occur because undigested fat must be eliminated from the body. During clinical trials, some patients experienced:

• Oily spotting
• Gas with oily discharge
• Fecal urgency
• Oily or fatty stools
• Increased bowel movements

These symptoms typically appear during the first month of treatment and often decrease as your body adjusts. Following a low-fat diet, where less than 30% of calories come from fat, may also reduce the likelihood and severity of these side effects.

Other common side effects may also include headaches, fatigue, and upper respiratory symptoms (such as cold and flu-like symptoms). Menstrual changes have also been reported, though a direct link is unclear.

While uncommon, some side effects require immediate medical attention. Contact your healthcare provider if you experience severe stomach pain, signs of liver problems (yellowing skin or eyes, dark urine, light-colored stools), symptoms of kidney issues, or allergic reactions such as difficulty breathing or swelling.

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How to Take Orlistat for Best Results

Take one capsule with each main meal that contains fat, up to three times per day. Orlistat should be taken during your meal or within one hour afterward. If you skip a meal or eat something fat-free, you can skip that dose.

It’s also important to keep your fat intake under 30% of your total daily calories to minimize digestive side effects. 

Yet, orlistat works best as part of a comprehensive approach. Combine the medication with a reduced-calorie diet and regular physical activity for optimal results. 

Because orlistat blocks fat absorption, it can also interfere with fat-soluble vitamins (A, D, E, and K). Studies show that orlistat can reduce vitamin E absorption. To prevent deficiencies, it’s usually recommended to take a daily multivitamin at least two hours before or after your orlistat dose.

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Where to Get Orlistat

Orlistat is available by prescription or over the counter, depending on your specific needs and the strength you require.

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Prescription Orlistat (Xenical®)

Xenical® contains 120 mg of orlistat and requires a prescription from a licensed healthcare provider. Your doctor will evaluate whether you meet the BMI requirements and assess any health conditions that may affect your eligibility. Once prescribed, you can fill it at local pharmacies or through a licensed online pharmacy.

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Over-the-Counter Orlistat (Alli®)

Alli® contains 60 mg of orlistat and is available without a prescription for adults 18 and older. You can purchase it at most pharmacies, drug stores, and major retailers.

When buying orlistat, especially online, always make sure you’re purchasing from reputable sources. Be cautious of counterfeit products or deals that seem too good to be true. If you’re unsure about where to buy, consult with a pharmacist or a licensed healthcare provider for better guidance.

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Drug Interactions With Orlistat

Orlistat can interact with several medications, potentially affecting their effectiveness. Before starting treatment, inform your healthcare provider about all medications you’re taking.

Some interactions worth noting include:

• Anticoagulants (blood thinners): Warfarin may require closer INR monitoring, as orlistat can affect vitamin K absorption and alter blood clotting.
• Antiepileptic medications: Orlistat may reduce the absorption of certain seizure medications, potentially decreasing their effectiveness.
• Immunosuppressants: Cyclosporine (a fat-soluble medication) absorption levels can be affected. Take it at least two hours apart from orlistat.
• Thyroid medications: Levothyroxine should be taken at least four hours before or after orlistat to ensure proper absorption.
• HIV antiretrovirals: Some medications may be less effective when taken with orlistat.

Since orlistat affects how your body absorbs nutrients and certain drugs, always disclose your full medication list, including over-the-counter drugs, vitamins, and supplements, to your healthcare provider before taking it.

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Final Thoughts

Orlistat is a scientifically supported option for weight management that works by blocking about 30% of dietary fat absorption. However, orlistat isn’t a quick fix. It works best as part of a comprehensive approach that includes healthy eating habits, consistent physical activity, and long-term lifestyle changes. It’s always best to discuss your options with a licensed healthcare provider first, since they can determine if orlistat makes sense for you and your specific situation.