Orlistat for Weight Loss: Uses, Side Effects, & Risks
Key takeaways:
Orlistat helps with weight loss by blocking dietary fat from being absorbed.
Common orlistat side effects include oily stools, urgent bowel movements, and stomach cramps.
Orlistat can reduce the absorption of essential vitamins, so a multivitamin supplement is often recommended.
It’s not suitable for everyone. Your GP can help determine if it’s right for you.
If you’re exploring weight loss treatments, you might have heard about orlistat. Orlistat is an oral medication designed to help with weight management when combined with healthy lifestyle changes.
But with any medicine, orlistat has potential risks and side effects. Common side effects include oily stools, stomach cramps, and flatulence. Long-term use can also lead to vitamin deficiencies and, in rare cases, kidney problems.
Let’s go over the side effects and risks of using orlistat, potential drug interactions, and safety tips.
What Is Orlistat?
Orlistat is a weight loss medicine that reduces the amount of fat your body absorbs. It belongs to a class of medicines called lipase inhibitors and is used to support weight management in people who are overweight or living with obesity.
In the United Kingdom, orlistat is available in two forms:
Xenical® (120 mg). This brand-name version of orlistat is available in the U.K. only with a prescription.
Alli® (60 mg). You can buy this non-prescription option online or from a chemist.
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How Does Orlistat Work for Weight Loss?
Normally, digestive enzymes (lipase) break down fat so your body can absorb it. Orlistat blocks lipase, so about a quarter to one-third of the fat you eat passes through undigested.
This lowers your calorie intake, supporting weight loss efforts and possibly improving obesity-related conditions like high blood pressure (hypertension), type 2 diabetes, and high cholesterol.
Research shows that people using orlistat lose more weight than those relying on diet and exercise alone. It may also reduce your chances of developing type 2 diabetes.
As with all weight loss medicines, orlistat is most effective when paired with a healthy, reduced-calorie diet and regular physical activity.
Side Effects of Orlistat
Orlistat, like any other drug, comes with risks and possible side effects. Most of the common side effects are mild, but there’s also a rare risk of serious side effects.
Common Orlistat Side Effects
Since undigested fat passes out of the body, the common side effects of orlistat include:
Oily or fatty stools
Oily spots on underwear
Urgent or frequent bowel movements
Flatulence (sometimes with discharge)
Stomach pain or cramps
These are typically mild and improve over time. But eating fatty meals increases the chances of experiencing these orlistat side effects.
Orlistat 120 mg Side Effects vs. 60 mg
Prescription-strength Xenical (120 mg) can cause more intense digestive side effects compared to Alli (60 mg). Following dietary advice can help minimise discomfort.
Rare but Serious Side Effects of Orlistat
Rare but possible reactions include:
Severe liver injury
Kidney stones
Allergic reaction (rash, itching, trouble breathing)
If you think you’re experiencing a serious side effect of orlistat, seek medical attention straight away.
Long-Term Side Effects of Orlistat
Over time, orlistat may reduce the absorption of fat-soluble vitamins (A, D, E, K). To avoid nutrient deficiencies, a multivitamin with beta-carotene is recommended — ideally taken at bedtime, away from orlistat doses.
You can report any side effects or adverse reactions to orlistat using the Yellow Card Scheme.
Is Orlistat Safe During Pregnancy?
No. If you’re pregnant or trying to conceive, you should avoid using orlistat.
There’s little research on the safety of orlistat while breastfeeding. While it’s unlikely your baby will absorb a significant amount of orlistat through breastmilk, use any medicine with caution while breastfeeding. Speak with your GP (general practitioner) if you’re considering using orlistat while nursing.
Also, since orlistat inhibits the absorption of fat-soluble vitamins, it’s especially important to take a multivitamin supplement if you’re breastfeeding.
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Orlistat Drug Interactions
Like many medicines, orlistat can interact with other treatments. These interactions may change how well your medications work or increase the risk of serious side effects.
Known orlistat drug interactions include:
Cyclosporine (used after organ transplant). Orlistat can reduce how much cyclosporine the body absorbs, lowering its effectiveness. If taken together, doses should be spaced at least three hours apart and carefully monitored.
Levothyroxine (for thyroid conditions). Taking orlistat at the same time as levothyroxine could reduce absorption of levothyroxine, leading to low thyroid levels. A GP might suggest spacing doses apart and monitoring thyroid function.
Warfarin and other blood thinners. Since orlistat can reduce absorption of vitamin K, it could affect blood clotting and alter how these medicines work. Clotting times may need close monitoring.
Other medicines. Orlistat can interfere with the absorption of some antiretrovirals (used for HIV treatment) and anti-seizure medications.
You can drink alcohol on orlistat, as there’s no direct drug interaction. But keep in mind that alcohol is calorie-dense and can undermine your weight loss attempts. Moderation is key.
To stay safe, tell your provider about all medicines and supplements you’re taking. Never start or stop medication without medical advice.
Who Shouldn’t Take Orlistat?
You shouldn’t take orlistat if:
You’re pregnant or trying to conceive
You have an eating disorder, such as bulimia or anorexia
You have trouble absorbing nutrients (chronic malabsorption syndrome)
You’ve had liver problems or kidney stones
You’re on medicines that are known to interact with orlistat (such as cyclosporine or levothyroxine
Always discuss with a healthcare professional before starting.
How to Take Orlistat Safely
To reduce the risk of side effects, take orlistat as directed. Here are some safety tips for taking orlistat:
Take orlistat with a main meal (up to 30 percent of your daily calories) that contains some fat.
If you skip a meal or eat a fat-free snack, skip that dose.
Don’t take more than three doses of orlistat per day.
Use orlistat with a reduced-calorie, low-fat diet to minimise side effects.
Take a multivitamin supplement containing vitamins A, D, E, K, and beta-carotene at bedtime.
Store orlistat at room temperature, out of reach of children or pets.
Remember, healthy lifestyle choices will enhance your weight loss efforts. Try to eat a balanced diet, exercise frequently, and maintain a regular sleep schedule — your body will thank you.
In Summary: Orlistat Side Effects
Together with a healthy diet and exercise routine, orlistat may help you reach a healthy body weight. Although it’s considered safe, the medicine comes with potential risks and side effects.
Here’s what to bear in mind:
Common orlistat side effects include oily stools, flatulence, and stomach cramps.
Rare but serious risks include kidney stones, liver problems, and allergic reactions.
Avoid orlistat if you’re pregnant, trying to conceive, or breastfeeding.
You may develop nutrient deficiencies if you’re on orlistat long-term. Reduce this risk by taking a daily supplement containing vitamins A, D, E, K, and beta-carotene.
Orlistat is generally considered safe. But, as with all medications, it’s not suitable for everyone. If you’re considering taking orlistat for weight loss, speak with a healthcare professional before starting.
Hers offers access to weight loss medications in the U.K. for those who are eligible, including GLP-1 drugs and oral medicines. Get started by taking our free quiz, and a U.K.-licensed provider will be in touch to discuss your treatment options.
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FAQs
See answers to commonly asked questions about orlistat for weight loss.
What does orlistat do?
Orlistat is a weight loss medication. It prevents the body from absorbing up to 30 percent of the fat you eat, helping reduce calorie intake.
Can you drink alcohol on orlistat?
Yes, you can, according to the Alli website. However, be mindful that alcoholic drinks can be high in calories, so they can undermine your weight loss efforts.
What happens if you take too much orlistat?
An extra dose of orlistat won’t accelerate weight loss. It may increase your risk of serious side effects, though. Your safest bet is to stick to the prescribed dose.
Can you take orlistat while breastfeeding?
If you want to use orlistat while breastfeeding, speak with your GP first. According to the Drugs and Lactation Database, orlistat is unlikely to affect a baby through breastmilk. But the medication’s safety during breastfeeding isn’t well-established.
Is orlistat available over the counter?
Yes. Alli® (60 mg) is available without a prescription. You can buy it online or from a pharmacy. Xenical® (120 mg) requires a prescription.
Do you need to take vitamins with orlistat?
Yes. A daily multivitamin with fat-soluble vitamins (A, D, E, K) is recommended with orlistat, taken at bedtime.
This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your GP about the risks and benefits of any treatment.