Semaglutide Injection (Ozempic/Wegovy)
Ozempic · Wegovy · Sema
Long-acting GLP-1 receptor agonist for type 2 diabetes and weight loss; weekly injection.
Key takeaways
- GLP-1 receptor agonist approved for type 2 diabetes (Ozempic) and weight management (Wegovy).
- ~7-day half-life; once-weekly subcutaneous injection, steady state in about 5 weeks.
- STEP trials showed ~15% mean weight loss at 68 weeks; SELECT added cardiovascular outcomes data.
- GI side effects are dose-dependent; 4-week titration steps are the management strategy.
Overview
What it is
Semaglutide (Ozempic for type 2 diabetes, Wegovy for weight management) is a GLP-1 receptor agonist that mimics the incretin hormone: it stimulates glucose-dependent insulin release, suppresses glucagon, slows gastric emptying, and reduces appetite centrally. A C18 fatty-diacid chain binds serum albumin, extending circulation far beyond native GLP-1's minutes-long life.
Pharmacokinetics
The ~7-day half-life enables once-weekly subcutaneous dosing, with steady state after about 5 weeks at each dose level. The label titrates every 4 weeks (0.25 → 0.5 → 1.0 → 1.7 → 2.4 mg for Wegovy) to manage dose-dependent GI effects.
What the evidence says
Among the best-evidenced compounds in the dataset: large phase 3 RCTs (STEP, SUSTAIN) showed ~15% mean weight loss at 68 weeks, and SELECT showed cardiovascular benefit. Weight regain follows discontinuation, so it manages a chronic condition rather than curing it.
Reported dosing protocols
Protocols reported in research literature and clinic/community use — informational context, not a dosing recommendation.
| Use case | Dose | Route | Frequency | Duration |
|---|---|---|---|---|
| Type 2 diabetes (Ozempic label) | 0.25 mg start, escalate to 0.5–2 mg | SubQ | Once weekly | Chronic |
| Weight management (Wegovy label) | 0.25 mg start, escalate q4wk to 2.4 mg | SubQ | Once weekly | Chronic |
Pharmacokinetic summary
- Model tier
- Advanced (t½ + Cmax + Tmax + F)
- Half-life
- 6.5 days
- Cmax
- 2879.1 nmol/L
- Tmax
- 1.3 days
- Bioavailability
- 89%
- Typical dose
- 0.25–2.4 mg
Frequently asked questions
Ozempic vs Wegovy: what's the difference?
Same molecule, same weekly injection; different labels and dose ceilings. Ozempic (0.5–2 mg) is approved for type 2 diabetes, Wegovy (up to 2.4 mg) for chronic weight management. Coverage follows the indication, which is why the branding split matters.
Why does semaglutide start at only 0.25 mg?
For tolerability, not effect. Nausea, vomiting, and diarrhea are dose-dependent, so the label escalates every 4 weeks to let the gut adapt. Skipping titration steps is the main reason reported experiences go badly.
What happens when you stop semaglutide?
STEP-1 extension data showed participants regained about two-thirds of lost weight within a year of stopping. Appetite and gastric-emptying effects reverse as the drug clears over 4–5 weeks, given the ~7-day half-life.
References
- PMC semaglutide PK
- Wilding et al., NEJM 2021 — STEP 1 — Phase 3 RCT: ~15% mean body-weight reduction at 2.4 mg over 68 weeks.
- FDA prescribing information (Wegovy) — Label titration schedule and dose ceiling for weight management.
Related compounds
Semaglutide Oral (Rybelsus)
Oral semaglutide with very low bioavailability; taken fasting.
Dulaglutide (Trulicity)
Long-acting GLP-1 agonist for type 2 diabetes and weight loss; weekly subcutaneous injection.
Tirzepatide (Mounjaro)
Dual GIP/GLP-1 agonist for weight loss and diabetes; weekly injection, strong efficacy.
Protocols featuring Semaglutide Injection (Ozempic/Wegovy)
Semaglutide Titration (20 weeks)
FDA Wegovy label titration: 0.25 → 0.5 → 1.0 → 1.7 → 2.4 mg weekly, escalating every 4 weeks to the 2.4mg maintenance dose.
CagriSema Titration (Cagrilintide + Semaglutide)
Investigational CagriSema combination (REDEFINE trial) — 16-week parallel titration of cagrilintide + semaglutide dosed weekly to the 2.4/2.4mg maintenance target.
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