PeptideInjectableIncretin agonistPeptideGLP-1
Semaglutide
Also known as Ozempic · Wegovy · Rybelsus
A once-weekly GLP-1 receptor agonist licensed for type 2 diabetes and obesity — the drug that defined the current weight-loss era. Large, well-evidenced weight loss with a gastrointestinal side-effect profile as the main limit.
01 Overview
Semaglutide agonises the GLP-1 receptor, slowing gastric emptying and reducing appetite centrally. Its trial evidence base is among the strongest of any compound on this site.
Tirzepatide edges it on raw weight loss in head-to-head data, but semaglutide has the longer safety record and cardiovascular-outcome data.
02 Mechanism
A GLP-1 analogue resistant to enzymatic degradation. Enhances glucose-dependent insulin secretion, slows gastric emptying, and reduces appetite via central pathways.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Starting | 0.25 mg/wk | SubQ | Four-week initiation dose to build tolerance. |
| Maintenance | 1–2.4 mg/wk | SubQ | Titrated up in monthly steps; 2.4 mg is the obesity dose. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Weight lossSTEP-1 trial at 2.4 mg | ~15% at 68 weeks | Clinical | |
| Glycaemic controlEstablished in type 2 diabetes | HbA1c −1.5 to −1.8% | Clinical | |
| Reduced cardiovascular eventsSELECT trial in overweight patients without diabetes | Significant | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Gastrointestinal effectsNausea, vomiting, diarrhoea and constipation — the dose-limiting effect and main reason for discontinuation. | Moderate | Very common | Clinical | |
| Lean mass lossA meaningful fraction of rapid weight loss is lean tissue. | Moderate | Common | Clinical |
06 Legal status
United States
Prescription only
FDA approved · as of Jan 2026
United Kingdom
Prescription only (POM)
as of Jan 2026
07 References
Once-weekly semaglutide in adults with overweight or obesity (STEP-1)N Engl J Med, 2021
Semaglutide and cardiovascular outcomes in obesity without diabetes (SELECT)N Engl J Med, 2023
08 Discussion0 comments
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This page is reference information, not medical advice. Doses and protocols are documented as they appear in the clinical literature and in practice — describing them is not a recommendation to use them. Countermeasures listed here are not a substitute for a physician. Legal status varies by jurisdiction and changes.