Several weight-loss medicines are available in the United States. About 5 to 10 pounds (lbs) (2 to 4.5 kilograms [kg]) can be lost by taking these medicines. But not everyone loses weight while taking them. Most people also regain the weight after they stop taking the medicines, unless they have made lasting lifestyle changes. These changes include exercising more, cutting unhealthy foods from their diets, and reducing the total amount they eat.

You may also see ads for herbal remedies and supplements that claim to help you lose weight. Many of these claims are not true. Some of these supplements can have serious side effects.

Note for women: Pregnant or nursing women should never take diet medicines. This includes prescription, herbal, and over-the-counter remedies. Over-the-counter refers to medicines, herbs, or supplements you can buy without a prescription.

The different weight-loss medicines are described below. Be sure to talk with your provider about which medicine is right for you.

ORLISTAT (XENICAL AND ALLI)

Orlistat works by slowing the absorption of fat in the intestine by about 30%. It is approved for long-term use.

About 6 lbs (3 kg) or up to 6% of body weight can be lost when using this medicine. But not everyone loses weight while taking it. Many people regain most of the weight within 2 years after they stop using it.

The most unpleasant side effect of orlistat is oily diarrhea that may leak from the anus. Eating fewer fatty foods can reduce this effect. Despite this side effect, most people tolerate this medicine.

Xenical is the brand of orlistat your provider can prescribe for you. You can also buy orlistat without a prescription under the name Alli. These pills are half the strength of Xenical. Orlistat costs about $100 or more a month. Consider whether the cost, side effects, and the small weight loss you can expect are worth it to you.

Your body may not absorb important vitamins, minerals, and other nutrients from food while you are using orlistat. You should take a daily multivitamin if you use orlistat.

MEDICINES THAT SUPPRESS THE APPETITE

These medicines work in your brain by making you less interested in food.

Not everyone loses weight while taking the medicines. Most people regain the weight after they stop taking the medicine unless they have made lasting lifestyle changes. Talk with your provider about how much weight you can expect to lose by taking any of these medicines.

These medicines are available only by prescription. They include:

• Benzphetamine, Phendimetrazine (Bontril, Obezine, Phendiet, Prelu-2)
• Diethylpropion (Tenuate)
• Liraglutide (Saxenda)
• Naltrexone combined with bupropion (Contrave)
• Phentermine (Adipex-P, Lomaira, Phentercot, Phentride, Pro-Fast)
• Phentermine combined with topiramate (Qsymia)
• Semaglutide (Wegovy)
• Setmelanotide (Imcivree)

Be sure you understand the side effects of weight-loss medicines. Side effects can include:

• Increase in blood pressure
• Problems sleeping, headache, nervousness, and palpitations
• Nausea, constipation, and dry mouth
• Depression, which some people who are obese struggle with already

If you have diabetes that needs treatment with medicines, you may want to ask your provider about diabetes medicines that often lead to weight-loss. These include:

• Canagliflozin (Invokana)
• Dapagliflozin (Farxiga)
• Dapagliflozin combined with saxagliptin (Qtern)
• Dulaglutide (Trulicity)
• Empagliflozin (Jardiance)
• Exenatide (Byetta, Bydureon)
• Liraglutide (Victoza)
• Lixisenatide (Adlyxin)
• Metformin (Glucophage, Glumetza, and Fortamet)
• Semaglutide (Ozempic)

Of these medicines, liraglutide and semaglutide are approved by the FDA to treat weight-loss in people without diabetes.

Prescription weight loss drugs; Diabetes - weight loss drugs; Obesity - weight loss drugs; Overweight - weight loss drugs

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Jensen MD. Obesity. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 207.

Maratos-Flier E. Obesity. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 40.

National Institutes of Diabetes and Digestive and Kidney Diseases website. Prescription medications to treat overweight & obesity. www.niddk.nih.gov/health-information/weight-management/prescription-medications-treat-overweight-obesity. Updated June 2021. Accessed July 8, 2023.

Updated by: Linda J. Vorvick, MD, Clinical Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.