Few medicines have drawn as much attention as the GLP-1 medications. They are discussed in clinics, in the news, and among friends, often with more enthusiasm than precision. This article sets out what they are, what they have been shown to do, and what they do not do, using federal sources.
What they are
GLP-1 stands for glucagon-like peptide-1, a hormone the body releases in response to food. Semaglutide and liraglutide mimic GLP-1. Tirzepatide mimics two hormones, GLP-1 and another called glucose-dependent insulinotropic polypeptide, or GIP.
These medicines act on areas of the brain that control appetite. Semaglutide also helps the pancreas release insulin when blood sugar is high and slows how quickly the stomach empties. Together, these effects can reduce appetite and lead to weight loss.
What they can do
They are approved for more than weight. Semaglutide, for example, is used to control blood sugar in certain people with type 2 diabetes, to reduce the risk of heart attack, stroke, or death in certain adults with heart disease, to reduce the risk of worsening kidney disease in certain adults with type 2 diabetes, to assist with weight loss in certain people with obesity or overweight and weight-related medical problems, and to treat a form of fatty liver disease called noncirrhotic MASH. Each use applies to specific groups of people, and the brand and dose differ by use.
They can produce meaningful weight loss alongside a lifestyle program. According to the National Institute of Diabetes and Digestive and Kidney Diseases, adults who take a weight-management medicine as part of a lifestyle program lose 3 to 12 percent more of their starting body weight after one year than people in a lifestyle program alone. Most of the weight loss happens in the first six months.
They are prescribed by defined criteria. Weight-management medicines may be prescribed for adults with a body mass index of 30 or higher, or 27 or higher with a weight-related condition such as high blood pressure or type 2 diabetes.
What they cannot do
They do not replace the work underneath. The NIDDK states that weight-management medicines work best when combined with a lifestyle program. They are not a substitute for nutrition, activity, and sleep.
They do not keep working after they stop. The NIDDK advises that you will probably regain some weight after stopping a weight-management medicine. If the medicine improves health without serious side effects, a clinician may advise staying on it long term.
They do not work for everyone. If a person has not lost at least 5 percent of her starting weight after 12 weeks at the full dose, her clinician will reassess, and may advise stopping.
They are not for everyone. These medicines should never be taken during pregnancy or when planning a pregnancy, and they are not recommended while breastfeeding. Semaglutide should be stopped two months before a planned pregnancy. People with a personal or family history of medullary thyroid cancer, or with Multiple Endocrine Neoplasia syndrome type 2, should not take semaglutide or tirzepatide. Both conditions are listed as contraindications in the prescribing information, because both medicines caused thyroid tumors in rats. Whether they raise that risk in humans is not known.
They can affect birth control pills. Tirzepatide slows how quickly the stomach empties, which can make birth control pills less effective. Its prescribing information advises switching to a method that is not taken by mouth, or adding a barrier method such as condoms, for 4 weeks after starting tirzepatide and for 4 weeks after each dose increase. Birth control that is not taken by mouth is not affected.
Side effects
The most common side effects are digestive: nausea, vomiting, diarrhea, constipation, stomach pain, heartburn, and burping. Headache is also common. Most side effects are mild and often improve with continued use.
Serious side effects are rare but real. Federal drug information advises getting prompt care for ongoing pain in the upper or middle stomach that may spread to the back, yellowing of the skin or eyes, decreased urination or swelling in the legs, signs of low blood sugar, vision changes, or a rapid heartbeat. Before starting, tell your clinician about any history of pancreatitis, gallbladder disease, or kidney disease.
A note on compounded and unapproved versions
The U.S. Food and Drug Administration has warned about unapproved GLP-1 products. Unapproved versions do not go through the FDA's review for safety, effectiveness, and quality. The agency has received reports of dosing errors with compounded injectable semaglutide, some requiring hospitalization, and has identified counterfeit and falsely labeled products in the U.S. supply.
The FDA's advice is direct. Obtain a prescription from a clinician, fill it at a state-licensed pharmacy, and use a compounded product only when an FDA-approved one cannot meet the medical need.
The honest summary
GLP-1 medications are a significant advance with several approved uses. They are most effective as one part of a broader plan, they require ongoing medical oversight, and they are not right for every person. A good evaluation asks whether one is indicated, what else is contributing, and who will monitor it, before the first dose.
The Energē Editorial answers one question like this each month, with sources printed in full. Join the Editorial.
If you are located in Virginia and would like your own picture evaluated, request an Energē Introduction.
This article is general education. It is not medical advice and does not replace care from your own clinician.
Sources
National Institute of Diabetes and Digestive and Kidney Diseases. Prescription Medications to Treat Overweight & Obesity. Last reviewed June 2024.
MedlinePlus, National Library of Medicine. Semaglutide Injection. Last revised May 15, 2026.
U.S. Food and Drug Administration. FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss. Current as of October 1, 2026.
U.S. Food and Drug Administration. Zepbound (tirzepatide) prescribing information. 2026.
