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Prescription weight-loss drugs

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Prescription weight-loss drugs

Study the pros and cons of medicines to treat obesity.

By Mayo Clinic Staff

Are you an adult who has serious health problems because of your weight? Have you tried diet and exercise but haven’t been able to lose enough weight? If you answered yes to these questions, a prescription weight-loss drug may be a choice for you.

Prescription drugs are medicines that a health care provider prescribes for you. You can’t buy them off the shelf in a drug store like you can buy nonprescription medicines.

Just know that you need to use prescription weight-loss drugs in addition to — not instead of — a healthy diet and exercise.

Who can take weight-loss drugs?

Your health care provider may suggest a weight-loss drug for you in some cases. These include if you haven’t been able to lose weight through diet and exercise and your:

  • Body mass index (BMI) is greater than 30. This means you’re living with a condition that involves having too much body fat, called obesity.
  • BMI is greater than 27. You also have a serious medical problem linked to obesity, such as diabetes or high blood pressure.

Before choosing a medicine for you, your health care provider thinks about your history and health challenges. Then your provider talks with you about the pros and cons of prescription weight-loss drugs.

These drugs aren’t for everyone. For example, you shouldn’t take prescription weight-loss drugs if you’re trying to get pregnant, are pregnant or are breastfeeding.

How well do weight-loss drugs work?

Prescription weight-loss drugs that you can use for more than 12 weeks, called long-term use, lead to major weight loss compared with an inactive treatment that doesn’t use medicine, called a placebo. The combination of weight-loss medicine and lifestyle changes leads to greater weight loss than do lifestyle changes alone.

Taking these drugs for a year can mean a loss of total body weight of 3% to 12% more than that lost with lifestyle changes alone. That may not seem like a lot. But losing 5% to 10% of your total weight and keeping it off can have important health benefits. For example, it can lower blood pressure, blood sugar levels and levels of fats in the blood called triglycerides.

What you should know about weight-loss drugs

Mild side effects, such as nausea, constipation and diarrhea, are common. They may lessen over time. Rarely, serious side effects can happen. That’s why it’s important to ask your health care provider about all treatment choices. And ask about the possible benefits and risks of each drug.

Weight-loss drugs can be expensive and aren’t always paid for by insurance. Ask your insurance company about your coverage.

Many people gain back some of the weight they lost when they stop taking weight-loss drugs. But practicing healthy lifestyle habits may help limit weight gain.

How long do I take a weight-loss drug?

How long you take a weight-loss drug depends on whether the drug helps you lose weight. If you’ve lost enough weight to improve your health and you haven’t had serious side effects, your health care provider may suggest that you take the drug long term.

If you haven’t lost at least 5% of your body weight after taking the full dose of a drug for 3 to 6 months, your health care provider will probably change your treatment. They may switch you to a different weight-loss drug.

What drugs are approved for weight loss?

Six weight-loss drugs have been approved by the U.S. Food and Drug Administration (FDA) for long-term use:

  • Bupropion-naltrexone (Contrave)
  • Liraglutide (Saxenda)
  • Orlistat (Xenical, Alli)
  • Phentermine-topiramate (Qsymia)
  • Semaglutide (Wegovy)
  • Setmelanotide (Imcivree)

Most prescription weight-loss drugs work by making you feel less hungry or fuller. Some do both. The exception is orlistat. It affects the way your body absorbs fat.


Bupropion-naltrexone is a combination drug. Naltrexone is used to treat alcohol and opioid addiction. Bupropion is a drug to treat depression, called an antidepressant, and a drug to help people stop smoking, called a quit-smoking aid. Like all antidepressants, bupropion carries a warning about suicide risk. Bupropion-naltrexone can raise blood pressure. So your provider will need to check your blood pressure regularly at the start of treatment. Common side effects include nausea, headache and constipation.


Liraglutide also is used to manage diabetes. It’s given as a daily shot. Nausea is a common complaint. Vomiting may limit its use.


You also can get orlistat in a reduced-strength form without a prescription (Alli). Orlistat can cause side effects such as passing gas and having loose stools. You need to follow a low-fat diet when taking this medicine. In rare cases, people have had serious liver injury with orlistat. But researchers haven’t found that the drug causes liver injuries.


Phentermine-topiramate is a combination of a weight-loss drug called phentermine and an anticonvulsant called topiramate. Phentermine has the potential to be misused because it acts like a stimulant drug called an amphetamine. Other possible side effects include an increase in heart rate and blood pressure, insomnia, constipation, and nervousness. Topiramate increases the risk of birth defects.

Phentermine by itself (Adipex-P, Lomaira) also is used for weight loss. It’s one of four similar weight-loss drugs approved for use for less than 12 weeks, called short-term use. The other drugs in this group aren’t often prescribed.


Semaglutide also is used to help control type 2 diabetes. You take it as a weekly shot to manage obesity.

It can cause side effects such as:

  • Nausea and vomiting
  • Diarrhea
  • Belly pain
  • Headache
  • Tiredness


The FDA has approved setmelanotide only for people age 6 and older who have obesity due to one of these rare inherited conditions:

  • Pro-opiomelanocortin deficiency
  • Proprotein subtilisin-kexin type 1 deficiency
  • Leptin receptor deficiency

To take the drug, you’ll need to have test results that show you have one of these conditions. Setmelanotide doesn’t treat any of the gene problems that cause these conditions. But it can help you lose weight. It can lessen your appetite and make you feel fuller. And it may help you burn calories while your body is at rest.

You take setmelanotide as a daily shot. It can cause side effects such as:

  • Swollen or irritated skin where the needle went in
  • Patches of darker skin
  • Nausea
  • Diarrhea
  • Belly pain
  • Unwanted sexual reactions
  • Depression
  • Suicidal thoughts

Never give setmelanotide to a child under 6 years old. It can cause newborns and babies to have dangerous reactions.

The bottom line

Weight-loss drugs aren’t an easy answer to weight loss. But they may help you make the lifestyle changes that you need to practice to lose weight and improve your health.

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Oct. 29, 2022

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