Semaglutide
GLP-1 receptor agonist
- Class
- GLP-1 agonist
- Half-life
- ~7 days
- Route
- Subcutaneous (SubQ)
- Cadence
- Weekly
- Evidence
- Human clinical trials
Overview
Semaglutide is the original GLP-1 weight-loss drug that started the current wave. You know it as Ozempic (for diabetes) or Wegovy (for weight management) — same molecule, different label. Newer drugs like tirzepatide and retatrutide produce more weight loss, but semaglutide has the most miles on the clock and the most robust safety record.
How it works: a single weekly injection that mimics the gut hormone GLP-1. The result is reduced appetite, slower stomach emptying, and better blood-sugar control. In the big weight-loss trial (STEP-1, 2021), people on the 2.4 mg dose lost about 15% of their body weight over 68 weeks. A separate trial (SELECT, 2023) showed that in people with cardiovascular disease, it cut the rate of heart attacks, strokes, and cardiovascular death by 20%.
The standard ramp takes 16 weeks. Most people who quit do so during the first month or two because of nausea, not long-term tolerability. Once you're past the ramp, side effects mostly settle. There's also an oral pill (Rybelsus), but at the doses currently sold it's only approved for diabetes, not weight management.
In January 2026, the European Medicines Agency's Committee for Medicinal Products for Human Use (CHMP) recommended conditional approval for semaglutide 2.4 mg to treat non-cirrhotic metabolic dysfunction-associated steatohepatitis (MASH), based on the ESSENCE Phase 3 programme showing reductions in liver inflammation and fibrosis.
Safety considerations
A few of the safety signals worth knowing — the full list, with dosing context and what to monitor, is inside AIx Core.
- Black-box warning for thyroid C-cell tumours (rat finding — unclear human relevance). Hard no if you or family have medullary thyroid carcinoma or MEN-2.
- Pancreatitis is rare but documented. Severe stomach pain that radiates to your back = stop and get evaluated.
- If you're diabetic and your HbA1c drops fast on semaglutide, diabetic retinopathy can transiently worsen. Worth a baseline eye exam if you've had retinopathy.
+ 3 more safety notes inside AIx Core →
Commonly monitored
Markers and signals people track when researching Semaglutide.
- Body weight and composition (not just scale — body recomposition matters)
- HbA1c if you have or are at risk for diabetes
- Lipid panel — most people see substantial improvement
- Gallbladder symptoms (right-upper abdominal pain, especially post-fatty-meal)
- Pancreatic enzymes (amylase, lipase) if you develop severe abdominal pain
Frequently asked questions
What is Semaglutide?
GLP-1 receptor agonist. Semaglutide is the original GLP-1 weight-loss drug that started the current wave. You know it as Ozempic (for diabetes) or Wegovy (for weight management) — same molecule, different label. Newer drugs like tirzepatide and retatrutide produce more weight loss, but semaglutide has the most miles on the clock and the most robust safety record.
How is Semaglutide administered?
Subcutaneous (SubQ), typically weekly.
What is the half-life of Semaglutide?
~7 days — Stays in your system about a week — once-weekly dosing.
Is Semaglutide approved for human use?
Semaglutide is approved by at least one regulator for one or more indications. Use outside an approved indication is off-label and not endorsed here.
What does the evidence show for Semaglutide?
Evidence tier: Human clinical trials. STEP-1 (Wilding 2021, N=1,961, 68 weeks): -14.9% body weight on 2.4 mg vs -2.4% on placebo. Less than tirzepatide but enormous compared to anything pre-2020.
What is commonly monitored when researching Semaglutide?
Commonly tracked markers + signals: Body weight and composition (not just scale — body recomposition matters), HbA1c if you have or are at risk for diabetes, Lipid panel — most people see substantial improvement, Gallbladder symptoms (right-upper abdominal pain, especially post-fatty-meal), Pancreatic enzymes (amylase, lipase) if you develop severe abdominal pain.
Related compounds
Open this in AIx Core for the full picture
Mechanism breakdown, receptor pathway diagram, full safety list, monitored items, source citations, and one-tap add-to-protocol. Free with any account.