Weight loss medications are prescription drugs that help people with overweight or obesity lose weight when lifestyle changes alone are not enough. These medicines work in different ways, such as reducing appetite or blocking fat absorption. Most people who use them as part of a healthy eating and activity plan lose more weight than with lifestyle changes alone. While most side effects are mild, some medicines can cause serious problems in rare cases. Working closely with a doctor helps ensure safe and effective use of these medications.

Weight loss medications are prescription drugs that aid in weight loss when diet and exercise alone have not been enough. These medicines are approved for adults and, in some cases, for children and teens with obesity or weight-related health problems.

There are several types of weight loss medications, each with different ways of helping people lose weight. Some are pills taken by mouth, while others are given as injections under the skin. The main goal of these medicines is to support healthy weight loss and improve health problems linked to overweight and obesity, such as high blood pressure, type 2 diabetes, and sleep apnea.

In the United States, more than 4 in 10 adults have obesity, and nearly 1 in 10 have severe obesity. Because obesity is a chronic disease that can lead to serious health problems, weight loss medications are an important option for people who need extra help reaching and maintaining a healthier weight.

Weight loss medications work by targeting different parts of the body to help reduce weight. Each medicine uses a specific approach to support weight loss, and some may be more effective for certain people than others.

Some medicines help people feel less hungry or feel full sooner. These include drugs that act on the brain to reduce appetite or increase feelings of fullness. Examples are phentermine-topiramate, naltrexone-bupropion, liraglutide, semaglutide, and tirzepatide. These medicines affect hormones or brain signals that control hunger and eating. GLP-1 medications, such as liraglutide and semaglutide, are a newer group of weight loss medications that work by mimicking a natural hormone in the body to help control appetite, increase feelings of fullness, and support healthy blood sugar levels. These medications are usually given as injections and have been shown to help people lose a significant amount of weight when combined with healthy lifestyle changes.

Other medicines, such as orlistat, work in the digestive system to block the absorption of some of the fat from food. By preventing the body from absorbing all the fat eaten, these medicines help lower calorie intake.

There are also medicines approved for rare genetic causes of obesity, such as setmelanotide, which targets specific pathways in the brain to decrease appetite and increase calorie use.

Most weight loss medications are used together with a reduced-calorie diet and increased physical activity. They are not meant to replace healthy eating and exercise but to support these efforts. The choice of medicine depends on a person’s health, other medicines they take, and their weight loss goals.

People who may benefit from weight loss medications are those who have not been able to lose enough weight with diet and exercise alone and/or have certain health risks. Doctors use body mass index (BMI), a measure of weight in relation to height, to help decide who should consider these medicines.

A good candidate for weight loss medications is usually:

• An adult with a BMI of 30 or higher, which is considered obesity
• An adult with a BMI of 27 or higher who also has weight-related health problems, such as high blood pressure, type 2 diabetes, or high cholesterol

Some medicines are also approved for children and teens ages 12 and older who have obesity, and for children as young as 6 with rare genetic conditions causing obesity.

Doctors consider other factors as well, such as a person’s overall health, other medicines they take, and their family medical history. Weight loss medications are not for everyone, and a doctor will help decide if they are a safe and appropriate choice.

Weight loss medications can help people lose more weight than with lifestyle changes alone, especially when combined with healthy eating and regular physical activity. These medicines can also improve health problems linked to overweight and obesity.

After one year, individuals who combine weight loss medication with a lifestyle program lose, on average, 3% to 12% more of their starting body weight than those who follow the lifestyle program alone. Some people lose 10% or more of their starting weight, depending on the medicine and individual response.

Losing 5% to 10% of starting body weight can lead to important health benefits, such as:

• Lowering blood sugar, which helps manage or prevent type 2 diabetes
• Reducing blood pressure, which lowers the risk of heart disease and stroke
• Improving cholesterol and triglyceride levels, which supports heart health
• Reducing joint pain, which can make movement easier
• Improving sleep apnea, which helps with better sleep and energy

Most weight loss happens in the first six months of starting the medicine. Keeping the weight off often requires ongoing use of the medicine along with continued healthy habits.

Weight loss medications can cause side effects, which vary depending on the specific medicine and how it works in the body. Most side effects are mild and improve over time, but some can be serious and may require stopping the medicine.

Common side effects include:

• Nausea
• Diarrhea
• Constipation
• Headache
• Dry mouth
• Insomnia
• Dizziness

Some medicines have unique side effects:

• Orlistat can cause oily or fatty stools, gas that may contain oily discharge, and an urgent need to use the bathroom, especially after high-fat meals
• Phentermine-topiramate may cause tingling in the hands or feet, changes in taste, and mood or attention problems
• Naltrexone-bupropion can cause constipation, nausea, vomiting, headache, insomnia, and dry mouth.
• Liraglutide, semaglutide, and tirzepatide can cause stomach pain, vomiting, and, rarely, gallbladder problems or pancreatitis

Serious side effects are rare but can include:

• Suicidal thoughts or actions, especially with some medicines
• Severe allergic reactions
• Heart problems
• Birth defects if taken during pregnancy, especially with phentermine-topiramate

People should contact their doctor right away if they have severe stomach pain, trouble breathing, chest pain, thoughts of self-harm, or signs of an allergic reaction. Doctors may stop or change the medicine if serious side effects occur.

Weight loss medications are not recommended during pregnancy or breastfeeding. Some medicines may interact with other drugs, so it is important to tell the doctor about all medicines, supplements, and vitamins being taken.

Weight loss medications are given in different ways, depending on the specific medicine. Some are taken by mouth as pills, while others are given as injections under the skin.

Common ways these medicines are given include:

• Pills taken by mouth once or several times a day, such as orlistat, phentermine-topiramate, and naltrexone-bupropion
• Injections given under the skin once a day or once a week, such as liraglutide, semaglutide, and tirzepatide

Doctors will explain how to take the medicine, including whether it should be taken with food or at a certain time of day. Some medicines, like orlistat, are taken with meals that contain fat. Others, like the injectable medicines, are given in the abdomen, thigh, or upper arm.

The doctor may start with a low dose and increase it slowly to help reduce side effects. If a person does not lose at least 5% of their starting weight after 12 weeks on the full dose, the doctor may recommend stopping the medicine or trying a different one.

Doctors monitor people taking weight loss medications to make sure the medicine is working and to watch for side effects. Regular check-ins help ensure safe and effective treatment.

Monitoring may include:

• Checking weight regularly to track progress
• Measuring blood pressure and heart rate, especially for medicines that can affect the heart
• Blood tests to check blood sugar, cholesterol, and kidney or liver function
• Asking about side effects or any new symptoms

Doctors may also review other medicines being taken to avoid harmful interactions. If serious side effects or health problems develop, the doctor may adjust the treatment plan or stop the medicine.

Most people who use weight loss medications as part of a healthy lifestyle program lose more weight and keep it off longer than with diet and exercise alone. With regular follow-up and support, many people find that weight loss medications help them reach and maintain a healthier weight, leading to better overall health and quality of life.

Individual results can vary. Some people lose a significant amount of weight and see major improvements in health problems like diabetes, high blood pressure, and sleep apnea. Others may lose less weight or have side effects that limit how long they can take the medicine.

Regaining weight can happen if the medicine is stopped, so long-term changes in eating and activity are important for maintaining weight loss. Doctors may recommend staying on the medicine as long as it is helping and not causing serious side effects.