Prescription weight loss medicines can help people with obesity lose weight. They are usually prescribed by a doctor when diet and exercise alone are not working. Each of these medicines works differently. People who use these medicines may not feel as hungry. Or they may feel full after eating only a small amount of food. Another type of weight-loss medicine makes it harder for your body to absorb fat. Prescription weight loss drugs can be helpful when used in combination with a low-calorie diet and regular physical activity.
Who uses prescription weight loss medicines?
Prescription weight-loss medicines are only for people who have obesity. Most of these medicines are designed for people who weigh 20% or more above what is ideal for their height and body type. Or they are used with people who have a high body mass index (BMI). The BMI is a measure of your weight in relation to your height. Your doctor may prescribe you medicine to treat your obesity if you have:
- A BMI of 30 or greater.
- A BMI of 27 or more and you have a disease or condition that may be related to your weight (this could include diabetes or high blood pressure).
Your doctor can tell you if prescription weight-loss medicines might be helpful for you.
Path to improved health
Prescription weight-loss medicines generally work in 2 ways. Most work in your body to make you less hungry or feel full faster. One FDA-approved medicine works in your digestive tract. It blocks the amount of fat your body can absorb. Some medicines are approved only for a short period of time, usually no more than 12 weeks. Others can be used long-term.
The following are medicines currently approved by the FDA for weight loss. Also included is information on how they work, common side effects, and warnings for each.
Orlistat
- Brand name: Xenical
- How it works: It reduces the amount of fat your body absorbs.
- Side effects: diarrhea, gas, uncontrollable bowel movements, leakage of oily stool
- Warnings: It can reduce the amount of certain vitamins that your body can absorb You should take a multivitamin pill every day.
Orlistat is also available in a lower dose without a prescription. That over-the-counter medicine is called Alli. Orlistat is the only medicine of its kind to be approved in the U.S.
The following medicines make you feel less hungry or full faster. They share common side effects, including constipation, dizziness, dry mouth, diarrhea, and nausea. Additional side effects are listed for each medicine.
Naltrexone-bupropion
- Brand name: Contrave
- How it works: It makes you less hungry or fuller faster.
- Side effects: headache, increased blood pressure and heart rate, insomnia, liver damage, vomiting
- Warnings: Don’t use if you have untreated high blood pressure, seizures, or a history of anorexia or bulimia. Don’t use if you are dependent on opioid pain medicines or are withdrawing from drugs or alcohol. Don’t use if you are already taking bupropion (brand names Wellbutrin, Zyban). This medicine could increase suicidal thoughts or actions.
Phentermine-topiramate
- Brand name: Qysmia
- How it works: It decreases appetite and makes you feel full sooner
- Side effects: taste changes (especially carbonated beverages), tingling of hands and feet, trouble sleeping
- Warnings: Tell your doctor if you have had a heart attack, stroke, abnormal heart rhythm, kidney disease, or mood disorder. Do not take if you have hyperthyroidism or glaucoma. This medicine could cause birth defects. Do not use if you are pregnant, planning to become pregnant, or breastfeeding.
Liraglutide
- Brand name: Saxenda
- How it works: It makes you feel less hungry or full sooner
- Side effects: abdominal pain, headache, increased pulse
- Warnings: It is available only by injection. Could increase the chance of developing pancreatitis.
Semiglutide
- Brand name: Wegovy and Ozempic
- How it works: It regulates your appetite to make you feel less hungry
- Side effects: nausea, diarrhea, indigestion, headache
- Warnings: It is an injection. Using this medicine could increase risk for thyroid tumors.
There are other medicines that can reduce your desire to eat. These include:
- Phentermine
- Benzphetamine
- Diethylpropion
- Phendimetrazine
These medicines are only FDA-approved to be used short-term, up to 12 weeks. They may only provide temporary weight loss. They have some side effects, too. These include:
- Difficulty sleeping
- Feeling nervous or restless
- Headache
- Raised blood pressure or pulse
You should not use these medicines if you have uncontrolled high blood pressure, heart disease, hyperthyroidism, or glaucoma. You should tell your doctor if you have anxiety or mood disorders before using these medicines.
In rare cases, some weight-loss medicines can cause serious liver injury. Call your doctor right away if you notice symptoms of liver injury, including:
- Itching skin
- Yellow eyes or skin
- Urine that is brown or dark-colored
- Pale-colored stool
- Loss of appetite
- Abdominal pain
Some weight-loss supplements containing ephedra, ephedrine, or caffeine are available without a prescription (over the counter). It is not known whether these medicines are safe. Such supplements have been linked to reports of heart attack, seizure, stroke, and death. It is important to talk to your doctor if you are taking or are considering taking an over-the-counter weight-loss supplement.
Things to consider
How can I avoid gaining weight back when I stop using the medicine?
There is no easy cure for being overweight. Prescription weight-loss medicines can help you get off to a good start. But once you stop taking them, the weight you lost may come back. To keep the weight off, you must eat a healthy diet and be physically active on a regular basis. You must continue these healthy habits even after you stop taking the medicine. Remember that losing weight and keeping it off is a lifelong effort.
How can I lose weight without taking a weight-loss medicine?
If you decide weight-loss medicines aren’t right for you, you can still meet your weight-loss goals. It’s important to develop healthy eating habits. But don’t expect to change everything overnight. Start by training yourself to eat without doing anything else at the same time. For example, don’t eat while you watch TV. Focus on what you’re eating. Try to eat slowly.
Next, change what and how much you eat. Your doctor can help you create a low-calorie or low-carb diet plan that will help you lose weight. They can offer tips for healthy snacking and portion control.
It is also important to be physically active. Regardless of your weight loss goal, the minimum recommended exercise for improving health is 30 minutes 5 times a week (for a total of 150 minutes per week). Regular exercise helps you burn calories faster, even when you are sitting still. Exercise also helps you burn fat and build muscle.
Aerobic exercise raises your heart rate and helps you burn calories. Examples of aerobic exercises include swimming, brisk walking, jogging, and bicycling. Anaerobic exercise, such as weight training, is also good because it adds muscle mass to your body. Muscle burns calories faster than fat.
Be sure to check with your family doctor before you begin an exercise program. They can help you create an exercise plan that will help you meet your goals.
Questions to ask your doctor
- What is my BMI?
- Do I meet the qualifications for weight-loss medicines?
- Which medicine is the right one for me?
- What are the side effects?
- Are the benefits of taking the medicine worth the risks and side effects?
- Will my insurance cover it?
- How long will I take it?
- Will I gain weight when I stop taking it?
- What can I do to prevent gaining weight?
Resources
Centers for Disease Control and Prevention: Healthy Weight, Nutrition, and Physical Activity
Last Updated:
This article was contributed by familydoctor.org editorial staff.
Copyright © American Academy of Family Physicians
This information provides a general overview and may not apply to everyone. Talk to your family doctor to find out if this information applies to you and to get more information on this subject.
