Key takeaways

  • Semaglutide is a prescription drug approved for type 2 diabetes, chronic weight management, heart risk reduction and a form of fatty liver disease.
  • In a large trial, adults with obesity lost about 15% of their body weight on average over 68 weeks.
  • Nausea and other stomach problems are the most common side effects, and most people regain weight after stopping.

Semaglutide copies a hormone called GLP-1 that your gut releases after you eat. GLP-1 tells the pancreas to release insulin when blood sugar rises, slows down how fast food leaves the stomach, and acts on parts of the brain that control hunger.

The natural hormone breaks down within minutes. Semaglutide was built to last much longer. A fatty-acid chain attached to the molecule lets it stay in the body for about a week.

What is semaglutide approved for?

In the U.S., semaglutide is approved to treat type 2 diabetes, for long-term weight management in adults with obesity or overweight and a weight-related condition, and to lower the risk of heart attack and stroke in certain people with heart disease. In 2025 the FDA also gave it accelerated approval for MASH, a type of fatty liver disease, in people with moderate to advanced liver scarring.

It comes as a weekly injection. A daily tablet for weight management was approved in December 2025.

What did the major trials find?

The STEP 1 trial followed about 2,000 adults with obesity for 68 weeks. People taking semaglutide lost an average of 14.9% of their body weight. People on placebo lost 2.4%. Both groups also got diet and exercise counseling.

The SELECT trial asked a different question: does it protect the heart? It enrolled over 17,000 people with heart disease and overweight who did not have diabetes. Those on semaglutide had a 20% lower rate of heart attack, stroke or cardiovascular death.

What happens when people stop?

Researchers followed STEP 1 participants for a year after the drug was stopped. On average they regained about two-thirds of the weight they had lost. Doctors generally treat semaglutide as a long-term medication for this reason.

Side effects and risks

  • Nausea, vomiting, diarrhea and constipation. These are most common in the first weeks of treatment.
  • Gallbladder problems and, less often, inflammation of the pancreas.
  • A boxed warning about thyroid C-cell tumors, based on studies in rodents. It is not known whether this applies to people.
  • Some of the weight lost is muscle rather than fat.

The FDA has also warned about unapproved and compounded versions of semaglutide, citing dosing errors and products that did not contain what the label said.

The bottom line

Semaglutide has some of the strongest evidence of any drug in this field, from trials involving tens of thousands of people. It also has real side effects and works only as long as people keep taking it. Whether it is a good fit is a decision for a patient and their doctor.

References

  1. Wilding JPH, et al. Once-weekly semaglutide in adults with overweight or obesity. N Engl J Med. 2021;384:989-1002.
  2. Lincoff AM, et al. Semaglutide and cardiovascular outcomes in obesity without diabetes. N Engl J Med. 2023;389:2221-2232.
  3. Wilding JPH, et al. Weight regain and cardiometabolic effects after withdrawal of semaglutide: the STEP 1 trial extension. Diabetes Obes Metab. 2022.
  4. U.S. Food and Drug Administration. Prescribing information for semaglutide products.