The Basics

Written by the doctors and editors at UpToDate

Can medicines help with weight loss?

Sometimes. Prescription weight loss medicines work by reducing your appetite or by changing how you digest food.

If you want to lose weight, start by talking to your doctor or nurse. They can help you make a plan to lose weight in a healthy way. The first step is to make changes to your diet and exercise habits. Sometimes, doctors recommend medicines in addition to these changes.

Doctors use a measure called "body mass index," or "BMI," to help understand a person's weight. Your BMI tells you which category you are in based on your weight and height (figure 1). Your doctor might recommend medicine if you have not been able to lose weight in other ways and you:

● Have a BMI of 30 or greater, or

● Have a BMI between 27 and 29.9, and also have a weight-related medical problem, like diabetes, heart disease, or high blood pressure

Doctors might also prescribe medicine in other cases. For example, if you carry extra weight in the belly area, you might be at higher risk for weight-related medical problems. Doctors sometimes recommend medicine in this situation if you also have certain health conditions.

If you are interested in trying medicine for weight loss, talk to your doctor or nurse. They can help you understand the benefits and risks.

What are the different weight loss medicines?

When doctors prescribe medicines for weight loss, they sometimes choose "GLP-1" medicines. This type of medicine was originally used for treating diabetes. But they can also help with weight loss in some people without diabetes. Examples include:

● Tirzepatide (sample brand names: Zepbound, Mounjaro)

● Semaglutide (sample brand names: Wegovy, Ozempic)

● Liraglutide (sample brand name: Saxenda)

● Orforglipron (brand name: Foundayo)

Most of these medicines come as a shot that goes under the skin. Semaglutide is available as a shot or a pill you take by mouth. Orforglipron only comes as a pill.

These medicines do not all work exactly the same way. But they all affect a hormone called GLP-1. They increase the amount of insulin your body releases after eating. (Insulin is a hormone that helps control blood sugar.) They also slow digestion and make you feel full more quickly.

For people who cannot take GLP-1 medicines, doctors sometimes recommend other medicines that come as pills. Examples include:

● Phentermine-topiramate (brand name: Qsymia)

● Naltrexone-bupropion (brand name: Contrave)

● Orlistat (brand names: Alli, Xenical)

● Phentermine (brand names: Adipex-P, Lomaira)

Do weight loss medicines cause side effects?

Yes. All these medicines can cause side effects.

Side effects depend on the medicine. For example, GLP-1 medicines can cause nausea, vomiting, diarrhea, and constipation. The other medicines can also cause other side effects.

Talk to your doctor about your medicine's possible side effects. You should also read all the information that comes with your prescription.

Can I reduce the cost of weight loss medicines?

Many weight loss medicines can be expensive. There are sometimes ways to lower the cost. For example, you can check the medicine company's website. They sometimes offer ways to buy the medicine from them directly, instead of getting it from a pharmacy.

Be careful about companies or websites offering "compounded" versions of weight loss medicines. These have risks. For example, they do not have to meet the same safety and quality requirements as other medicines.

If you are worried about cost, or if you have questions about other ways to get your medicine, ask your doctor or nurse.

What else should I know?

● Weight loss medicines can be a helpful part of treatment for some people. But even if your doctor does prescribe medicine, they will also still recommend making lifestyle changes. This can help improve your overall health.

● For most medicines to work, you probably need to keep taking them long term. Otherwise, you will likely gain back the weight you lose.

● If you take medicine that can cause weight gain to treat a health condition, your doctor can work with you to try to find one that will not cause weight gain. This can be an important part of a weight loss plan.

● Be careful about herbs and supplements that claim to help with weight loss. Many of these do not work, and some are unsafe. Check with your doctor or pharmacist before you take any non-prescription ("over-the-counter") medicines for weight loss.

● If you take a GLP-1 medicine and are planning surgery, talk to your doctor. They might recommend stopping the medicine ahead of time. That's because these medicines can increase the risk of food or liquid getting into the lungs. This can happen if there is anything in the stomach when a person gets anesthesia.

All topics are updated as new evidence becomes available and our peer review process is complete.

This topic retrieved from UpToDate on: Apr 15, 2026.

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Images

figure 1: Your body mass index (BMI)

Find your height (in feet and inches) in the top row. Then, find your weight (in pounds) in the first column. Now, find where the column for your height and the row for your weight meet. That is your BMI. For example, if you are 5-feet-9-inches tall and you weigh 260 pounds, your BMI is 38.

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