Semaglutide
Weight Loss, Metabolic Health
In short
- An FDA-approved GLP-1 receptor agonist — one of the very few compounds in this library that is an actual licensed medicine with large randomised trials behind it.
- Approved for type 2 diabetes (Ozempic, Rybelsus) and chronic weight management (Wegovy), with cardiovascular benefit demonstrated in dedicated outcome trials.
- Roughly one-week half-life, which is what allows once-weekly dosing and also means levels take 4–5 weeks to plateau after any change.
- Gastrointestinal side effects are common and dose-related; titration exists specifically to manage them.
- Compounded and grey-market semaglutide is not the approved product and has been the subject of repeated FDA warnings about dosing errors and unverified salt forms.
Structure
How it works
Semaglutide is a modified analogue of human GLP-1, an incretin hormone released from the gut after eating. Substitutions at position 8 resist DPP-4 degradation, and a C18 fatty diacid chain drives albumin binding — together these extend the half-life from GLP-1's couple of minutes to about a week.
Activating the GLP-1 receptor increases glucose-dependent insulin secretion, suppresses glucagon, and slows gastric emptying. The weight effect is driven substantially through receptors in the hypothalamus and hindbrain that reduce appetite and food reward. Glucose-dependence is why it carries low intrinsic hypoglycaemia risk when used alone.
What the research shows
In the STEP programme, weekly semaglutide 2.4 mg produced roughly 15% mean body-weight reduction over 68 weeks versus about 2.4% on placebo. In SUSTAIN, HbA1c reductions were consistently superior to comparator agents.
SELECT demonstrated a 20% reduction in major adverse cardiovascular events in people with overweight or obesity and established cardiovascular disease but without diabetes — the result that moved it from a metabolic drug to a cardiovascular one.
Weight regain after discontinuation is well documented: STEP 1 extension showed participants regained about two-thirds of lost weight within a year of stopping.
Dosing in the literature
Figures below are quoted from published studies, with the species or population they were measured in. They are records of what was studied, not recommendations.
| Studied in | Amount | Route | Source |
|---|---|---|---|
| Human — type 2 diabetes (Ozempic), approved label | 0.25 mg weekly for 4 weeks, then 0.5–2.0 mg weekly | subcutaneous | FDA label |
| Human — chronic weight management (Wegovy), approved label | Titrated monthly: 0.25 → 0.5 → 1.0 → 1.7 → 2.4 mg weekly | subcutaneous | FDA label |
| Human — oral formulation (Rybelsus), approved label | 3 mg daily for 30 days, then 7–14 mg daily | oral | FDA label |
Commonly reported ranges
These are amounts people report using. They are not from any study, have not been evaluated for safety, and are reproduced here only because they circulate widely and are better seen alongside the evidence than instead of it.
No commonly reported ranges for this compound.
This is an approved medicine with a published label — the titration schedule exists to limit gastrointestinal effects and is not optional decoration. Dosing should come from the prescribing clinician and the label, not from this page.
Handling and storage
The approved products are supplied as prefilled pens with fixed dose steps. Rotate injection sites between abdomen, thigh, and upper arm. Any day of the week works provided the interval stays roughly seven days.
Compounded vials require reconstitution and manual measurement, which is where the reported dosing errors come from — the FDA has documented overdoses of 5–20× intended when people confused units on an insulin syringe with milligrams.
Side effects
Nausea, vomiting, diarrhoea, and constipation are the most common and are dose-related, usually worst after each escalation and settling with time. Slow titration is the primary mitigation.
Serious but uncommon: pancreatitis, gallbladder disease (more likely with rapid weight loss), and diabetic retinopathy complications in people with pre-existing retinopathy and rapid glucose improvement.
Carries a boxed warning for thyroid C-cell tumours based on rodent data; contraindicated with personal or family history of medullary thyroid carcinoma or MEN2. Rodent relevance to humans is unresolved.
Gastroparesis and delayed gastric emptying have become a recognised concern, with anaesthesia guidance now addressing aspiration risk from retained stomach contents.
Combinations
Cagrilintide (an amylin analogue) is under active study alongside semaglutide as CagriSema, with trial data showing greater weight reduction than either alone.
Combination with insulin or sulfonylureas raises hypoglycaemia risk and normally requires dose reduction of those agents — a genuine interaction, not a theoretical one.
Stacking with other GLP-1 or GIP agonists (tirzepatide, retatrutide) duplicates the same pathway and multiplies gastrointestinal effects without evidence of benefit.
Research status
One of the most heavily studied compounds in modern metabolic medicine: SUSTAIN (diabetes), STEP (obesity), SELECT (cardiovascular outcomes), plus ongoing trials in heart failure with preserved ejection fraction, chronic kidney disease, and neurodegenerative disease.
The evidence base here is categorically different from the rest of this library — large, randomised, placebo-controlled, and independently replicated.
Legal status
FDA-approved and prescription-only in the United States, and similarly regulated in the EU, UK, Australia, and Canada. Selling it without a prescription is illegal in these jurisdictions. Compounded versions were permitted during the official shortage; the FDA declared the shortage resolved in 2025, which removed most legal grounds for compounding it.
WADA status
Not currently prohibited by WADA. GLP-1 agonists are not on the Prohibited List as of this review date. Verify against the live list before competition, as it is reissued each January.
Conclusion
Semaglutide is the compound in this library with the strongest evidence and the clearest regulatory position, and the one where obtaining it outside the prescription system carries the most avoidable risk. The molecule is well characterised; the grey-market supply chain is not.
If you are using it, the titration schedule and the gastrointestinal timeline are the two things most worth respecting.
Sources
- [1]DailyMed — semaglutide prescribing information (Ozempic, Wegovy, Rybelsus)FDA label
- [2]STEP programme — semaglutide 2.4 mg in obesityPubMed
- [3]SELECT — cardiovascular outcomes with semaglutidePubMed
- [4]FDA — risks of compounded semaglutide and dosing errorsFDA
- [5]PubChem CID 56843331PubChem
- [6]WADA Prohibited List (current)WADA
Track your own Semaglutide protocol
Peppers logs your doses, models your levels from this half-life, tracks your vials and tells you when you will run out. Free on iPhone.
Reference and educational information only. Not medical advice. Nothing here diagnoses, treats, or prescribes, and nothing here is a recommendation to use any compound. The compounds described are research chemicals and are not approved for human consumption. Legal and anti-doping status change — the review date above is when these claims were last checked. Talk to a qualified clinician about anything you intend to take.