Semaglutide: The GLP-1 Peptide Behind 15% Body-Weight Loss
Semaglutide reshaped metabolic medicine. It mimics the gut hormone GLP-1 to slow gastric emptying, suppress appetite, and improve glycemic control.
Semaglutide is a long-acting GLP-1 receptor agonist sold under brand names Ozempic and Wegovy. Trials show consistent 14–17% body-weight loss over 68 weeks at the 2.4 mg weekly dose — the largest effect ever recorded for a pharmacological obesity treatment before tirzepatide.
Mechanism: Why GLP-1 Works
GLP-1 is released by L-cells in the gut after a meal. It tells the pancreas to release insulin, the stomach to empty more slowly, and the hypothalamus to register satiety. Endogenous GLP-1 breaks down within minutes; semaglutide has been engineered with a fatty acid tail that binds to albumin, extending its half-life to about 7 days. One injection per week is enough to keep the receptor saturated.
Typical Titration
Standard titration starts at 0.25 mg weekly for 4 weeks to acclimate the gut, then doubles roughly every 4 weeks: 0.5 mg → 1 mg → 1.7 mg → 2.4 mg. Most side effects (nausea, constipation) appear during titration and resolve once a stable dose is reached. Skipping the slow ramp is the single most common reason people quit.
Side Effects to Plan For
Nausea is near-universal in the first weeks. Constipation, fatigue, and a transient drop in muscle mass are also common — the muscle loss is largely from eating less, not the peptide itself, and can be mitigated with adequate protein (~1.6 g/kg) and resistance training. Rare but serious risks include pancreatitis and gallbladder issues.
Reference page
Reconstitution chart, dose calculator, and storage notes for this peptide.
Open the reference cardFAQ
- How fast does semaglutide work for weight loss?
- Appetite suppression typically appears within the first week. Meaningful weight loss begins around weeks 4–8 and continues for 12+ months on the maintenance dose.
- Can you keep weight off after stopping semaglutide?
- Trials show roughly two-thirds of lost weight returns within a year of stopping if no other intervention is made. Most clinicians treat it as a long-term medication.