GLP-1 medicines have become some of the most talked-about drugs in the world. Originally developed for type 2 diabetes, they now also treat obesity and help protect the heart, kidneys and more. This guide explains how they work, how the best-known brands differ, and what to expect if your doctor suggests one.
How GLP-1 medicines work
GLP-1 (glucagon-like peptide-1) is a hormone your gut releases after eating. GLP-1 medicines mimic it. They:
- Help the pancreas release insulin when blood sugar is high
- Reduce the liver’s release of glucose
- Slow the emptying of the stomach, so you feel full sooner and for longer
- Act on appetite centers in the brain to reduce hunger and food cravings
Because they boost insulin only when glucose is high, they rarely cause low blood sugar on their own.
The main medicines
| Medicine | Brand names | Main uses | How it is taken |
|---|---|---|---|
| Semaglutide | Ozempic | Type 2 diabetes | Weekly injection |
| Semaglutide | Rybelsus | Type 2 diabetes | Daily tablet |
| Semaglutide | Wegovy | Chronic weight management; lowering heart risk in people with heart disease and obesity | Weekly injection |
| Tirzepatide | Mounjaro | Type 2 diabetes | Weekly injection |
| Tirzepatide | Zepbound | Chronic weight management; obstructive sleep apnea with obesity | Weekly injection |
| Liraglutide | Victoza, Saxenda | Type 2 diabetes; weight management | Daily injection |
| Dulaglutide | Trulicity | Type 2 diabetes | Weekly injection |
Tirzepatide is technically a dual GIP and GLP-1 agonist. It acts on two gut hormones, which is one reason it tends to produce greater weight loss.
How much weight do people lose?
In major clinical trials, people with obesity who took semaglutide 2.4 mg (Wegovy) lost about 15 percent of their body weight on average over roughly 68 weeks. People taking the highest dose of tirzepatide (Zepbound) lost around 20 percent over 72 weeks. Results vary widely between individuals, and the trials combined medication with diet and activity advice.
Benefits beyond weight and blood sugar
- Heart protection: semaglutide reduced heart attacks, strokes and cardiovascular deaths in people with heart disease and obesity in a large trial, and several GLP-1 drugs reduce cardiovascular events in people with type 2 diabetes.
- Kidneys: semaglutide has been shown to slow kidney disease progression in people with type 2 diabetes.
- Sleep apnea: tirzepatide is approved for obstructive sleep apnea in adults with obesity.
- Fatty liver: semaglutide is approved for a form of fatty liver disease with liver scarring (MASH).
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Common side effects
Most side effects affect the digestive system and are worst when starting or increasing the dose:
- Nausea
- Vomiting
- Diarrhea or constipation
- Indigestion, burping and bloating
- Reduced appetite
Doctors start with a low dose and increase it slowly over weeks to months to reduce these effects. Eating smaller meals, stopping when full, avoiding greasy food and drinking enough water helps.
Serious but less common risks
- Pancreatitis: severe stomach pain that spreads to the back, with or without vomiting, needs urgent medical care.
- Gallbladder problems, including gallstones, particularly with rapid weight loss.
- Dehydration and kidney problems if vomiting or diarrhea is severe.
- Low blood sugar when combined with insulin or sulfonylureas.
- Thyroid tumor warning: these drugs caused thyroid C-cell tumors in rodents. It is not known whether this happens in humans, but they should not be used by people with a personal or family history of medullary thyroid cancer or the genetic condition MEN2.
- Worsening diabetic eye disease in some people whose blood sugar falls quickly.
- Muscle loss: some of the weight lost is muscle. Eating enough protein and doing strength training helps protect it.
Tell your doctor or anesthetist that you take a GLP-1 medicine before any surgery or procedure that needs sedation, because slower stomach emptying can affect safety.
Who can take them?
For weight management, the FDA-approved criteria are generally a body mass index (BMI) of 30 or higher, or 27 or higher with at least one weight-related condition such as high blood pressure, type 2 diabetes or high cholesterol. They are not recommended during pregnancy, and women trying to conceive are usually advised to stop them beforehand.
What happens if you stop?
Obesity is a chronic condition, and these medicines work only while you take them. In studies, many people regained a large part of the lost weight within a year of stopping. Some people move to a lower maintenance dose. Building habits around nutrition, activity and sleep while on treatment makes it easier to maintain results.
Compounded and online versions
During past shortages, compounded versions of semaglutide and tirzepatide were widely sold. These are not FDA-approved, and the FDA has warned about dosing errors and products of uncertain quality. Buy only from licensed pharmacies with a valid prescription, and be wary of websites selling “research” peptides or offering the drugs without a medical consultation.
Cost and insurance
These medicines are expensive at list price. Coverage for type 2 diabetes is common, but coverage for weight loss varies widely between insurers and employers. Medicare does not cover drugs used only for weight loss, but it can cover Wegovy when it is prescribed to reduce cardiovascular risk in eligible patients, and Zepbound for sleep apnea. Manufacturer savings programs and direct-pay pricing may help. Check with your plan and pharmacist.
The bottom line
GLP-1 medicines are powerful tools for type 2 diabetes and obesity, with growing evidence of benefits for the heart, kidneys and liver. Most side effects are digestive and improve with slow dose increases. They work best alongside healthy eating, strength training and long-term follow-up with your doctor.
This article is for general information and does not replace medical advice. Do not start, stop or change any medicine without talking to your doctor.