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alli weight loss relies on orlistat 60 mg, an FDA-approved over-the-counter drug that blocks some of the fat you eat from being absorbed. It is not a dietary supplement. Its Drug Facts label says it is for overweight adults 18 and older who follow a reduced-calorie, low-fat diet, and that in studies most people lost 5 to 10 pounds over 6 months. This guide explains how orlistat works, what trials found, the diet rules and bowel side effects, vitamin advice, drug interactions, the 2010 liver warning and how alli compares with prescription Xenical.
Everything here comes from the alli Drug Facts label and the Xenical prescribing information on DailyMed, plus FDA announcements. It is general information, not medical advice.
Key Takeaways
- alli is an FDA-approved OTC drug containing orlistat 60 mg; Xenical is the prescription 120 mg version.
- Orlistat blocks gut enzymes that digest fat, so some dietary fat passes out of the body unabsorbed.
- The label says most people lost 5 to 10 pounds over 6 months when combined with diet.
- A low-fat diet is required; high-fat meals make oily spotting and urgent bowel movements more likely.
- Take a daily multivitamin at bedtime and check with a doctor or pharmacist about interactions first.
What is alli?
alli is the brand name for orlistat 60 mg capsules, made by Haleon. FDA approved it for nonprescription sale on February 7, 2007, and at the time the agency’s head of over-the-counter drugs called it the only FDA-approved, over-the-counter weight-loss drug product. That is still the case: Kaiser Permanente’s health library, updated in 2026, states that orlistat (alli) is the only over-the-counter weight-loss product approved by FDA.
Because alli is a drug, it went through FDA review for safety and effectiveness and carries a Drug Facts label. Weight-loss supplements do not go through that review. We list alli alongside our supplement guides for convenience, but it follows drug rules.
How orlistat works
Orlistat is a lipase inhibitor. Lipases are enzymes in the stomach and small intestine that break down dietary fat (triglycerides) into pieces the body can absorb. Orlistat binds to these enzymes inside the gut, so part of the fat in a meal passes through undigested and leaves in the stool. According to the Xenical prescribing information, the 120 mg prescription dose blocks about 30% of dietary fat absorption. The alli label simply says orlistat stops the absorption of some of the fat you eat.
It works on fat only. It does not block carbohydrates or protein, and it does little when a meal contains no fat.
Who the alli label is for
The label limits use to overweight adults aged 18 and older, together with a reduced-calorie, low-fat diet and exercise. A height and weight chart on the package shows the minimum weight for each height. The label also lists who should not use it or should ask first:
- Do not use if you have had an organ transplant, take cyclosporine, have been diagnosed with problems absorbing food, are allergic to any ingredient or are not overweight.
- Do not use if you are pregnant or breastfeeding.
- Ask a doctor first if you have ever had gallbladder problems, kidney disease or kidney stones, or pancreatitis.
- Ask a doctor or pharmacist first if you take blood thinners, amiodarone, diabetes, thyroid or seizure medicine, HIV medicines or other weight-loss products.
alli weight loss results: what studies found
The alli label puts it plainly: for every 5 pounds you lose from diet alone, orlistat can help you lose 2 to 3 pounds more, and most people in studies lost 5 to 10 pounds over 6 months. Most weight loss happens in the first 6 months, and the label notes that weight may return after stopping.
Longer data come from Xenical at twice the dose. In the four-year XENDOS trial of 3,304 adults with obesity, average weight loss was 5.17% with Xenical and 2.75% with placebo, both alongside diet, a difference of about 2.5 percentage points. Only 52% of the Xenical group and 34% of the placebo group completed the study. The prescribing information adds that long-term effects on illness and death linked to obesity have not been established. Results vary widely from person to person.
The low-fat diet and bowel side effects
Because unabsorbed fat leaves in the stool, the label warns of bowel changes: gas with oily spotting, loose stools and more frequent stools that may be hard to control. It advises starting a reduced-calorie, low-fat diet before taking the first capsule, and says a low-fat diet lowers the chance of these effects. The Xenical information describes a diet with about 30% of calories from fat, spread over three main meals.
Directions for when and how many capsules to take are on the label and in the brochure inside the pack. Follow them, and do not go over the daily limit.
Vitamin advice on the label
Orlistat can reduce the absorption of some vitamins. The alli label tells users to take a multivitamin once a day, at bedtime. The Xenical prescribing information is more specific: the multivitamin should contain vitamins A, D, E and K and beta-carotene, and it should be taken at least 2 hours before or after orlistat.
Drug interactions to discuss first
Orlistat can change how well some medicines work. This table summarizes what the alli label and the Xenical prescribing information say:
| Medicine | What the labels say |
|---|---|
| Cyclosporine (transplant medicine) | alli: do not use. Xenical: lowers cyclosporine levels; doses must be separated by 3 hours |
| Levothyroxine (thyroid medicine) | alli: ask first. Xenical: take at least 4 hours apart and monitor thyroid function |
| Warfarin and other blood thinners | alli: ask first. Xenical: monitor clotting tests closely |
| Amiodarone (heart rhythm medicine) | alli: ask first. Xenical: lower amiodarone exposure seen |
| Seizure medicines | alli: ask first; stop and call a doctor if seizures increase. Xenical: convulsions reported |
| HIV antiretrovirals | alli: ask first. Xenical: loss of viral control reported; monitor HIV levels |
| Diabetes medicines | alli: ask first. Xenical: diabetes medicine doses may need adjusting as weight falls |
Liver and kidney warnings, including the 2010 label update
On May 26, 2010, FDA announced it had finished a safety review of orlistat and severe liver injury. It found 13 reports between April 1999 and August 2009, 12 from outside the U.S. with Xenical and 1 in the U.S. with alli, among an estimated 40 million users worldwide. FDA said a cause-and-effect link had not been established, but it added the information to both labels.
The current alli label says to stop and ask a doctor if you develop itching, yellow eyes or skin, dark urine or loss of appetite, noting rare reports of liver injury. It also mentions rare reports of kidney injury: stop and ask a doctor if you have severe back or groin pain, painful urination, blood in your urine, swollen legs or feet, or you urinate less often than normal. Severe or continuous abdominal pain is another reason to stop and get medical advice.
alli vs Xenical
alli and Xenical contain the same active ingredient at different strengths and for different users:
| alli | Xenical | |
|---|---|---|
| Active ingredient | Orlistat 60 mg | Orlistat 120 mg |
| How you get it | Over the counter | Prescription |
| Who it is for | Overweight adults 18 and older | Adults with obesity (BMI 30 or more, or 27 or more with risk factors) |
| Diet required | Reduced-calorie, low-fat diet | Reduced-calorie diet with about 30% of calories from fat |
| Supervision | Self-selected using the Drug Facts label | Prescribed and monitored by a clinician |
Newer prescription medicines work very differently from orlistat; see our comparison of semaglutide vs tirzepatide. For the difference between drugs and supplements that borrow drug names, read what GLP-1 support supplements are.
Buying alli
We carry the alli orlistat 60 mg 170-capsule refill pack. Before buying, check the height and weight chart, read the full Drug Facts label and the enclosed brochure, and ask a pharmacist if you take any prescription medicine. The label says to store it at room temperature, away from excess light, humidity and heat.
Frequently Asked Questions
Is alli a supplement or a drug?
alli is an FDA-approved over-the-counter drug. It carries a Drug Facts label and went through FDA review, unlike dietary supplements.
How much weight can you lose with alli?
The label says most people in studies lost 5 to 10 pounds over 6 months, and that orlistat can add 2 to 3 pounds of loss for every 5 pounds lost through diet alone. Individual results vary.
What is the difference between alli and Xenical?
Both contain orlistat. alli is 60 mg and sold over the counter to overweight adults; Xenical is 120 mg and prescribed for adults with obesity.
What are the side effects of orlistat?
The most common are bowel changes: gas with oily spotting, loose stools and frequent stools that may be hard to control. A low-fat diet makes them less likely. Rare liver and kidney injury have been reported.
Do I need to take vitamins with alli?
Yes. The label says to take a multivitamin once a day at bedtime, because orlistat can reduce the absorption of some vitamins.
Can I take alli with levothyroxine or warfarin?
Ask your doctor or pharmacist first. The labels say orlistat can affect thyroid medicine and blood thinners, and doses or monitoring may need to change.
Who should not take alli?
People who have had an organ transplant, take cyclosporine, have problems absorbing food, are not overweight, or are pregnant or breastfeeding should not use it.
alli is an over-the-counter drug. Read and follow the Drug Facts label and the enclosed brochure, and ask a doctor or pharmacist before use if you take prescription medicines or have a medical condition. This article does not replace advice from your healthcare provider. Questions? Contact us.
Last reviewed September 2026.