What Is Semaglutide? (Ozempic, Wegovy, Rybelsus)

Semaglutide is a GLP-1 receptor agonist — a medication that mimics the natural GLP-1 gut hormone to reduce appetite, slow digestion, and regulate blood sugar. It is sold under three brand names: Ozempic (injectable, approved for type 2 diabetes), Wegovy (injectable, approved for weight management and MASH), and Rybelsus (oral tablet, approved for type 2 diabetes). All three contain the same active molecule at different doses and formulations.

How does semaglutide work?

Semaglutide binds to the GLP-1 receptor — the same receptor that the body's own GLP-1 hormone uses. This triggers a cascade of effects:

• Reduced appetite. Semaglutide acts on appetite-regulating centres in the brain, reducing hunger signals and cravings. People on semaglutide typically feel full sooner and eat less without consciously restricting intake.
• Slowed gastric emptying. Food moves from the stomach into the small intestine more slowly. This extends the sensation of fullness after eating and blunts post-meal blood sugar spikes.
• Glucose-dependent insulin stimulation. Semaglutide signals the pancreas to release insulin when blood sugar rises — but only when it is actually elevated. This makes hypoglycaemia (low blood sugar) less likely than with some older diabetes medications.

Unlike the natural GLP-1 hormone, which degrades within minutes, semaglutide is engineered with a fatty acid chain attached to its structure. This protects it from degradation and allows it to last approximately one week in the body — which is why injectable semaglutide is dosed once weekly. For a broader overview of how this class of drugs works, see: What Is a GLP-1?

The three brand names: what's different?

The active molecule in all three is identical. The differences are dose, formulation, and approved indication. The higher maximum dose of Wegovy reflects the clinical requirements of the weight-management indication. Rybelsus uses a special formulation with a permeation enhancer (SNAC) that allows oral semaglutide to be absorbed through the stomach lining — most peptide drugs would be broken down by digestive enzymes before reaching the bloodstream. See: The Wegovy Pill (Oral Semaglutide): What to Know.

Is Ozempic the same as Wegovy?

Yes and no. The same active molecule — but different approved indications, different dosing schedules, and different maximum doses. Ozempic is approved for type 2 diabetes management; Wegovy is approved for chronic weight management (and, since 2025, for MASH with liver fibrosis).

In practice, some people receive Ozempic prescribed off-label for weight loss — this is a prescriber decision made in the context of individual patient care. The regulatory distinction matters for insurance coverage and formulary placement, but the pharmacology of the molecule is the same. See: Ozempic vs Wegovy vs Mounjaro vs Zepbound.

How does semaglutide compare to tirzepatide?

Semaglutide targets only the GLP-1 receptor. Tirzepatide (Mounjaro, Zepbound) targets both the GLP-1 receptor and the GIP receptor — a dual mechanism. In the SURMOUNT-5 head-to-head trial, tirzepatide produced greater average weight loss than semaglutide. However, individual responses vary considerably, and the right choice depends on your medical history and your clinician's assessment. See: Tirzepatide vs Semaglutide for Weight Loss.

What about muscle loss on semaglutide?

Semaglutide reduces appetite significantly, which reduces calorie intake. Without adequate protein and resistance exercise, a meaningful share of the weight lost can be lean muscle rather than fat. This applies on any GLP-1 medication. The muscle-protection approach is the same on semaglutide as on any other drug in this class: hit your protein target, do resistance training, and consider creatine. See: Ozempic Side Effects: The Nutrition Angle.

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