GLP-1 Agonists (Overview)
GLP-1 receptor agonists · Incretin mimetics · Semaglutide class
The drug class that changed obesity medicine forever. From Ozempic to Mounjaro — the full landscape.
What is GLP-1 Agonists (Overview)?
GLP-1 receptor agonists are the most significant pharmaceutical development in obesity and metabolic medicine in decades. They mimic GLP-1 (glucagon-like peptide-1), a gut hormone that regulates appetite, insulin secretion, and gastric emptying. The result: profound appetite suppression, significant weight loss, improved blood sugar control, and — increasingly — cardiovascular protection.
What started with exenatide (Byetta) in 2005 has evolved into a multi-billion-pound drug class. Semaglutide (Ozempic/Wegovy), liraglutide (Saxenda), tirzepatide (Mounjaro/Zepbound), and next-generation compounds are transforming how medicine approaches obesity, diabetes, NAFLD, cardiovascular disease, and potentially even neurodegeneration.
This is not a single drug entry — it is an overview of the entire class, comparing mechanisms, efficacy, and the research pipeline. Individual compound pages for semaglutide and tirzepatide contain deeper details on those specific drugs.
How Does It Work?
All GLP-1 agonists bind the GLP-1 receptor, but their pharmacological profiles differ:
1. Appetite suppression — GLP-1 acts on hypothalamic appetite centres to reduce hunger. The effect is dose-dependent and varies by compound. 2. Gastric emptying — slowed, so food stays in the stomach longer. This contributes to fullness but also to the nausea side effect. 3. Insulin secretion — enhanced in a glucose-dependent manner (only works when blood sugar is elevated, reducing hypoglycaemia risk). 4. Glucagon suppression — reduces liver glucose output. 5. Cardiovascular effects — reduced inflammation, improved endothelial function, direct cardioprotection.
Dual agonists (tirzepatide: GLP-1 + GIP) and triple agonists (retatrutide: GLP-1 + GIP + glucagon) represent the next evolution, targeting multiple metabolic pathways simultaneously.
What Does The Research Say?
Strong clinical evidence from human trials.
The evidence base is enormous:
Semaglutide (Wegovy): 14.9% weight loss over 68 weeks (STEP 1). 20% cardiovascular event reduction (SELECT trial). Tirzepatide (Zepbound): 22.5% weight loss (SURMOUNT-1). Potentially superior to semaglutide. Retatrutide (triple agonist): 24.2% weight loss in Phase II — the highest ever recorded for a pharmaceutical. Orforglipron: oral non-peptide GLP-1 agonist in development — could replace injections entirely.
Beyond weight loss: trials underway for Alzheimer's, NAFLD/NASH, sleep apnoea, polycystic kidney disease, and addiction. The GLP-1 receptor is expressed in the brain, liver, kidneys, heart, and gut — the therapeutic potential is vast.
The key debate: weight regain upon cessation. Most studies show 60-70% of weight is regained within a year of stopping. This suggests long-term or indefinite use may be necessary, which raises cost and supply concerns.
Reported Dosages
These are dosages reported in research literature and community reports. They are NOT medical recommendations. Always consult a healthcare professional.
All GLP-1 agonists are prescription-only and require medical supervision.
Semaglutide: 0.25mg to 2.4mg weekly injection (titrated over 16 weeks).
Liraglutide: 0.6mg to 3.0mg daily injection.
Tirzepatide: 2.5mg to 15mg weekly injection.
Dulaglutide: 0.75mg to 4.5mg weekly injection.
Oral semaglutide (Rybelsus): 3mg to 14mg daily tablet.
Do NOT use without medical supervision. Compounded versions from non-pharmaceutical sources carry significant quality and safety risks.
Side Effects & Risks
Class-wide: nausea (20-40%, usually transient), vomiting, diarrhea, constipation. These improve with slow dose titration.
Serious (rare): pancreatitis, gallbladder disease, thyroid tumours (rodent studies — unclear human relevance, but contraindicated with personal/family history of medullary thyroid cancer).
Muscle loss: a significant concern. GLP-1 agonists cause approximately 25-40% lean mass loss as a proportion of total weight lost. Resistance training and adequate protein intake (1.6g/kg) are strongly recommended alongside.
"Ozempic face": rapid facial fat loss causing a gaunt appearance. More common with higher doses and faster weight loss.
Legal Status by Country
Prescription only. Multiple drugs approved (Ozempic, Wegovy, Saxenda, Mounjaro). NHS availability varies.
Prescription only. FDA-approved. Supply shortages ongoing for some formulations.
Prescription only. EMA-approved.
Prescription only. PBS-listed for diabetes. Weight management access varies.
Important Disclaimer
This profile is for educational and research purposes only. It does not constitute medical advice. GLP-1 Agonists (Overview) may be regulated or illegal in your jurisdiction. Do not use any compound without consulting a qualified healthcare professional. StackPedia does not sell, supply, or promote the use of any controlled substance.