How GLP-1 medications work, who they’re for, and what to ask before starting.
Ozempic, Wegovy, and Zepbound often come up in the same conversation. The name they’re grouped under, GLP-1, actually refers to a hormone your body releases after you eat. Some prescription medicines mimic that hormone’s effects. Depending on the product, they can help manage type 2 diabetes or support long-term weight management.
What is GLP-1?
GLP-1 stands for glucagon-like peptide-1. It’s a hormone made in the gut that helps coordinate what happens after a meal.
- It helps regulate blood sugar. When blood sugar rises, GLP-1 helps the pancreas release insulin. It also reduces the release of glucagon, a hormone that tells the liver to release stored glucose.
- It slows stomach emptying. Food moves from the stomach into the small intestine more slowly.
- It helps you feel full. GLP-1 acts on pathways that regulate appetite and food intake.
Prescription GLP-1 receptor agonists activate the same receptors. The effects can help lower blood sugar in type 2 diabetes and make it easier for some people to eat less. NIH overview of weight-management medicines
How do semaglutide and tirzepatide differ?
Semaglutide and liraglutide target the GLP-1 receptor. Tirzepatide targets two receptors, GLP-1 and GIP. GIP is another hormone involved in the body’s response to food. That’s why you’ll sometimes see tirzepatide described as a dual GIP and GLP-1 receptor agonist. NIH medication comparison
| Active ingredient | How it works | U.S. brand examples for type 2 diabetes | U.S. brand examples for weight management |
|---|---|---|---|
| Semaglutide | Activates GLP-1 receptors | Ozempic, Rybelsus | Wegovy |
| Liraglutide | Activates GLP-1 receptors | Victoza | Saxenda |
| Tirzepatide | Activates GIP and GLP-1 receptors | Mounjaro | Zepbound |
These are examples of approved uses. Some products have additional indications. Even when two brands share an active ingredient, the dose, formulation, and instructions can differ. Ask your prescriber or pharmacist before switching products. NIH medication comparison
Who might be eligible?
For weight management, common U.S. prescribing criteria for adults include a body mass index (BMI) of at least 30, or a BMI of at least 27 with a weight-related health condition such as high blood pressure or type 2 diabetes. A clinician also considers your medical history, treatment goals, other medicines, and the risks of the specific product.
For type 2 diabetes, the decision starts with your diabetes treatment goals and the product’s approved use. If you already take insulin or a sulfonylurea, your care team may adjust your treatment or ask you to monitor your blood sugar more closely. Combining these drugs can increase the risk of low blood sugar. NIH eligibility overview · FDA Wegovy prescribing information
What can you expect when starting?
Many of these medicines start at a low dose that increases in steps. This gives your body time to adjust. Ask your prescriber what to do if side effects are still bothering you when the next increase is due, or if you miss a dose. Instructions vary by product.
Your follow-up may cover appetite, weight, blood sugar, side effects, and whether you can keep up with meals and fluids. For weight management, these medicines are used alongside changes in eating and physical activity. Cost, coverage, and access are worth discussing early because they affect whether you can continue treatment. FDA Wegovy prescribing information · NIH weight-management overview
Side effects and when to get help
Nausea, vomiting, diarrhea, constipation, and abdominal discomfort are common. Contact your prescriber if symptoms persist, interfere with eating or drinking, or worsen after a dose increase.
Get urgent medical advice for severe belly pain that doesn’t go away, especially if it spreads to your back, or if repeated vomiting leaves you unable to keep fluids down. These medicines carry warnings about pancreatitis, gallbladder problems, and kidney injury related to dehydration. Seek emergency care if you have trouble breathing or swelling of the face, lips, tongue, or throat. FDA Wegovy prescribing information
Before starting, tell your clinician if you have severe gastroparesis (delayed stomach emptying), a history of pancreatitis, or diabetic eye disease. Mention any upcoming procedure involving anesthesia or deep sedation. If you’re pregnant or planning a pregnancy, discuss the timing and your treatment options with your prescriber. Weight-loss medications are generally avoided during pregnancy. FDA Wegovy prescribing information
What about the thyroid warning? Wegovy and Zepbound carry boxed warnings based on thyroid tumors seen in animal studies. Whether they cause these tumors in humans is unknown. The labels say people with a personal or family history of medullary thyroid carcinoma, or with multiple endocrine neoplasia type 2 (MEN2), should not use these products. FDA Wegovy prescribing information · FDA Zepbound prescribing information
What happens if you stop taking it?
Weight regain is possible. In an extension of the STEP 1 trial, participants who had received semaglutide regained, on average, about two-thirds of the weight they had lost one year after the medication and structured lifestyle intervention ended. Individual experiences vary. If you’re considering stopping because of side effects, cost, or another reason, talk with your prescriber about a plan for maintaining progress or managing blood sugar. STEP 1 trial extension
Are compounded GLP-1 drugs and “GLP-1 support” supplements the same?
A compounded drug is prepared for a particular clinical need. The FDA does not review compounded products for safety, quality, or effectiveness before marketing. It has reported dosing errors with compounded injectable GLP-1 products and warns against products sold directly to consumers as “research use only.” If your prescriber recommends a compounded version, ask why an approved product can’t meet your needs and confirm the pharmacy is state-licensed. FDA guidance on unapproved GLP-1 drugs
Products marketed as “GLP-1 support” supplements are a separate category. The phrase on a label does not establish that the product acts like a prescription GLP-1 medication or produces comparable results.
Five questions to ask your clinician
- Which medication fits my health goals, and how will we measure progress?
- Do any of my current medications or medical conditions change the risks?
- How will the dose increase, and what should I do if side effects interfere with meals or fluids?
- Which symptoms should prompt a call or urgent medical care?
- What’s the plan if I need to switch or stop treatment?