Orlistat: What It Is and How to Use It Safely

Orlistat (brand names Xenical for prescription and Alli for OTC) helps people lose weight by blocking some dietary fat from being absorbed. It doesn’t suppress appetite or burn fat—it keeps about 25–30% of the fat in a meal from being taken up by your body. That means it works best when you also eat fewer calories and move more.

How Orlistat Works and Dosing

Prescription orlistat is usually 120 mg taken with each main meal containing fat, up to three times a day. The OTC version (Alli) is 60 mg with meals. Take the pill during or within one hour after the meal. If you skip a meal or the meal has no fat, skip the dose.

To get results, combine orlistat with a reduced-calorie, lower-fat diet. Aim for meals where fat is spread across the day rather than one very fatty meal. Weight loss tends to be modest—many people lose a few percent of their body weight over several months—but even small losses can improve blood pressure and blood sugar.

Side Effects, Risks & Practical Tips

The most common effects are gastrointestinal: oily or loose stools, urgent bowel movements, gas with oily discharge, and more frequent bowel motions. These happen because undigested fat leaves your gut. You can reduce these by eating lower-fat meals and avoiding large fatty dishes. If you find side effects too disruptive, lowering meal fat usually helps quickly.

Because orlistat reduces absorption of fat-soluble vitamins (A, D, E, K), take a daily multivitamin at bedtime or at least 2 hours after orlistat. That keeps vitamin levels normal while you’re on the drug.

Don’t use orlistat if you’re pregnant, breastfeeding, or have chronic malabsorption (like chronic pancreatitis) or cholestasis. Tell your doctor if you have a history of gallbladder problems, organ transplant, or severe liver disease—there have been rare reports of liver injury linked to orlistat.

Some medicines can be affected. Orlistat may lower absorption of cyclosporine and thyroid hormone (levothyroxine); spacing doses or monitoring blood levels is needed. If you take warfarin, your INR might change—ask your doctor about extra monitoring.

Small, practical tips: keep meals moderate in fat and spread fat across the day; carry wet wipes or spare clothes if you’re nervous about urgent symptoms; take a multivitamin at night; and weigh yourself weekly to track progress. If you have severe stomach pain, yellowing skin, dark urine, or unexpected bleeding, stop orlistat and contact your doctor right away.

Orlistat can be a helpful tool if you need extra help losing weight, but it works best with diet changes and regular activity. Talk with your healthcare provider about whether it fits your health profile and how to use it safely with any other meds you take.