Semaglutide: Science & Profile
Last updated July 2, 2026 · Medically reviewed by David Chen, MD, PhD
Semaglutide is the foundational compound of the GLP-1 class and the benchmark against which newer agonists are measured. It is a single molecule that mimics GLP-1, the gut hormone that curbs appetite and slows gastric emptying — engineered to last in the body so a single weekly injection sustains the effect.
Semaglutide Science
GLP-1 is a hormone your body already makes to regulate hunger and insulin response. Semaglutide is a single molecule that mimics this hormone, so its effect is sustained over time.
What the trials show
In the STEP 1 trial (2021), participants lost roughly 14.9% of body weight at the 2.4 mg dose over 68 weeks. Beyond weight, the SELECT trial (2023) found about a 20% reduction in major cardiovascular events, and semaglutide has a long-established record of lowering HbA1c in type 2 diabetes.
How it is dosed
Clinical protocols start low — 0.25 mg once weekly — and step up every four weeks to a maintenance dose of 2.4 mg, easing the gastrointestinal side effects that come with starting too fast. You can model the full escalation schedule and projected weight loss in the dosing calculator.
Status and side effects
Sold under the brand names Ozempic, Wegovy, and Rybelsus, semaglutide is FDA-approved for both diabetes and obesity. The most common side effects are gastrointestinal — nausea, vomiting, and diarrhea — usually worst during escalation and easing at maintenance. See the full side-effect breakdown or compare semaglutide directly against tirzepatide and retatrutide.
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