Semaglutide is one of the most talked-about medicines of the past few years, sold under the brand names Ozempic, Wegovy and Rybelsus. It is a peptide drug that copies a natural gut hormone called GLP-1. This guide explains, in plain English, what semaglutide does in the body, what it is approved for, and what to know about safety.
Key takeaways
- Semaglutide is a GLP-1 receptor agonist, a lab-made version of a hormone your gut releases after meals.
- It helps the body release insulin when blood sugar is high, lowers glucagon, slows stomach emptying and reduces appetite.
- FDA-approved brands include Ozempic and Rybelsus (type 2 diabetes) and Wegovy (weight management and heart risk reduction, among other uses).
- It lasts about a week in the body, which is why the injection is weekly.
- Your prescriber chooses the product, dose and schedule. Doses start low and go up gradually.
What is GLP-1?
GLP-1 stands for glucagon-like peptide-1. It is a hormone your intestines release when you eat. It sends several "you've eaten" signals:
- Tells the pancreas to release insulin when blood sugar is rising
- Tells the pancreas to release less glucagon, a hormone that raises blood sugar
- Slows how fast food leaves the stomach
- Acts on the brain to help you feel full
Natural GLP-1 only lasts a couple of minutes before an enzyme called DPP-4 breaks it down. That is too short to work as a medicine. Semaglutide was designed to last much longer.
How semaglutide is built to last
According to the Ozempic prescribing information, semaglutide has 94% sequence similarity to human GLP-1. A few changes make it different:
- It resists breakdown by the DPP-4 enzyme.
- It has a fatty side chain that lets it attach to albumin, a common protein in the blood. This slows how fast the kidneys clear it.
The result is an elimination half-life of about one week. The label notes that semaglutide stays in circulation for about five weeks after the last dose. This is why the injections are given once a week and why side effects can linger for a while after stopping.
What it does in the body
Blood sugar
Semaglutide boosts insulin release and lowers glucagon in a glucose-dependent way. That means it mainly works when blood sugar is high. On its own, it has a low risk of causing low blood sugar. The risk goes up when it is combined with insulin or medicines called sulfonylureas, so prescribers may adjust those.
Appetite and fullness
GLP-1 receptors in the brain help control hunger and fullness. Many people on semaglutide notice they feel full sooner and think about food less. Slower stomach emptying adds to that feeling, especially early on.
Heart, kidneys and more
Large clinical trials have studied semaglutide beyond blood sugar and weight. Based on those trials, FDA has approved certain semaglutide products to lower the risk of major heart events in specific groups of people, and Ozempic to lower certain kidney risks in adults with type 2 diabetes and chronic kidney disease.
FDA-approved semaglutide products
| Brand | Form | Main FDA-approved uses (adults unless noted) |
|---|---|---|
| Ozempic | Weekly injection pen | Type 2 diabetes blood sugar control; lowering heart risks in type 2 diabetes with heart disease; lowering kidney and heart risks in type 2 diabetes with chronic kidney disease |
| Rybelsus | Daily tablet | Type 2 diabetes blood sugar control; heart risk reduction in certain high-risk adults with type 2 diabetes |
| Wegovy injection | Weekly injection pen | Weight reduction and maintenance (adults and children 12+); lowering heart risks in adults with heart disease and obesity or overweight; MASH liver disease with moderate to advanced scarring |
| Wegovy pill | Daily tablet (approved December 2025) | Weight reduction and maintenance; heart risk reduction |
A higher-strength Wegovy injection was also approved in 2026 for some adults who already tolerate the standard top dose. Labels change over time, so check the current prescribing information or ask your pharmacist. You can also see our semaglutide profile.
How doses are set
Every semaglutide product starts at a low dose and increases step by step over weeks. This is called titration, and it helps the stomach adjust. The exact steps differ by product and by person. Your prescriber sets your dose and schedule. PepSteady does not recommend doses.
The Ozempic label says if you miss a weekly dose, take it as soon as possible within 5 days; if more than 5 days have passed, skip it and take the next dose on your usual day. Other products have their own rules, so check yours.
Side effects and safety
Common side effects
The most common side effects are stomach-related: nausea, vomiting, diarrhea, stomach pain and constipation. They are most likely when starting or increasing a dose. Eating smaller meals, stopping when full and staying hydrated are common tips. Our guide on GLP-1 side effects goes deeper.
Boxed warning
Semaglutide labels carry a boxed warning about thyroid C-cell tumors seen in rodents. It is not known if this happens in people. Semaglutide should not be used by people with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).
Other warnings
Labels also list pancreatitis, gallbladder problems, low blood sugar when used with certain diabetes medicines, kidney problems from dehydration, allergic reactions and eye changes in some people with diabetes. Tell your prescriber about all your conditions and medicines, and let them know if you are pregnant, planning pregnancy or breastfeeding.
Brand-name vs. compounded semaglutide
FDA declared the semaglutide shortage resolved in February 2025, which limited when pharmacies may make copies. In April 2026, FDA also proposed excluding semaglutide from the list of bulk ingredients large outsourcing facilities may use. Compounded versions are not FDA-approved. If you are offered one, talk with your prescriber and pharmacist about why, and read our post on brand-name vs. compounded GLP-1s.
Tracking your progress
Doses go up over time, side effects come and go, and weight is only one measure of progress. Logging doses, symptoms, meals, protein and measurements in the PepSteady app makes it easier to spot patterns and share them with your prescriber.
The bottom line
Semaglutide copies the GLP-1 hormone but lasts about a week, which lets it lower blood sugar, reduce appetite and, in studied groups, lower heart risk. It comes in several FDA-approved brands with different uses. Work with your prescriber on the right product and dose, and keep them updated on how you feel.
Sources
- DailyMed: Ozempic (semaglutide) prescribing information
- Novo Nordisk: Wegovy pill approved in the US (December 2025)
- FDA: Proposal to exclude semaglutide, tirzepatide and liraglutide from the 503B bulks list
- FDA: Resolution of shortages of semaglutide injection products
Frequently asked questions
Is semaglutide the same as Ozempic and Wegovy?
Semaglutide is the active ingredient. Ozempic, Wegovy and Rybelsus are FDA-approved brand-name products that contain it, each approved for specific uses, forms and doses.
How long does semaglutide stay in the body?
According to the Ozempic label, semaglutide has an elimination half-life of about one week and stays in the bloodstream for about five weeks after the last dose. That long half-life is why the injection is given once a week.
What are the most common side effects?
Stomach-related effects are the most common, especially nausea, vomiting, diarrhea, stomach pain and constipation. They tend to show up as doses are increased. Your prescriber can explain what to watch for and when to call.