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Weight-loss medicines


Several weight-loss medicines are available. Ask your health care provider if any are right for you.

About 5 to 10 pounds (2 to 4.5 kilograms) 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, such as exercising and cutting unhealthy foods from their diets.

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.

Medicine Options


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

About 6 pounds (3 kilograms) 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 less fatty foods can reduce this effect. Despite this side effect, most people tolerate this medicine.

Xenical is the brand of orlistat your health care 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.


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:

  • Phentermine (Adipex, Fastin, Ionamin, Phentercot, Phentride, Pro-Fast, and Suprenza)
  • Phentermine combined with topiramate (Qsymia)
  • Benzphetamine (Didrex)
  • Phendimetrazine (Bontril, Melfiat, Obezine, Phendiet, and Prelu-2)
  • Diethylpropion (Tenuate)
  • Naltrexone combined with bupropion (Contrave)
  • Lorcaserin (Belviq)

Only lorcaserin and phentermine/topiramate are approved for long-term use. All other drugs are approved for short-term use of no more than a few weeks.

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 many people who are obese struggle with already

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

  • Canagliflozin (Invokana)
  • Dapagliflozin (Farxiga)
  • Exenatide (Byetta, Bydureon)
  • Liraglutide (Victoza)
  • Metformin (Glucophage, Glumetza, and Fortamet)

These medicines are not approved by the FDA to treat weight-loss. So you should not take them if you do not have diabetes.


Jensen MD. Obesity. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 220.

Waller DG, Sampson AP, Renwick AG, Hillier K. Obesity. In: Waller DG, Sampson AP, Renwick AG, Hillier K. Medical Pharmacology and Therapeutics. 4th ed. Philadelphia, PA: Elsevier Saunders; 2014:chap 37.

Review Date:5/3/2015
Reviewed By:Laura J. Martin, MD, MPH, ABIM Board Certified in internal medicine and hospice and palliative medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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