GLP-1 Agonist / SubQ, Oral / 0.25-2.4mg weekly
Semaglutide
Semaglutide is a designed analog of the gut hormone GLP-1, engineered at Novo Nordisk to survive a full week in circulation by binding tightly to blood albumin. Approved for diabetes in 2017 and obesity in 2021, it outgrew its own manufacturing within months, and shortage-era compounding plus a research-chemical vial market became a large share of how people actually obtain it.
In plain words
Semaglutide is a lab-made version of GLP-1, a natural gut hormone, redesigned so that one injection lasts about a week. It is an approved prescription medicine, cleared in the United States for type 2 diabetes in 2017 and for weight management in 2021. The evidence behind it is strong: large randomized trials found a mean 14.9 percent body-weight reduction over 68 weeks against 2.4 percent on placebo, better blood sugar control, and fewer heart attacks and strokes in people at high cardiovascular risk. Stomach and gut upset is the main side effect, with nausea reported by 44.2 percent of people in the weight-loss trial against 17.4 percent on placebo. Long-term stimulation of this receptor caused thyroid tumors in rats and mice; that has not been shown in people, but US labels carry it as a boxed warning. Demand outran manufacturing almost immediately, so a large share of what people actually use comes from compounded or research-chemical vials rather than a pharmacy pen, and outside regulated manufacturing the purity of the peptide and the sterility of the fill are what vary.
At a glance
| Half-life | 6.5 days |
|---|---|
| Tmax | 1.25 days |
| Route(s) | SubQ, Oral |
| Published dosing range | 0.25-2.4mg weekly |
| Vial strengths | 5, 2, 10 mg |
Reference data from the DosePlot canon -- not a protocol recommendation.
Serum curve
Single 1.33 mg dose by SubQ, rendered from the same engine that powers the interactive chart. Relative levels, not lab values.
What does the evidence show?
Two things are labeled separately here because they answer different questions. The tier is how a study was built. The distance chips are whether that study touched this molecule, by this route, in a population resembling the reader. A randomized trial of a different molecule keeps its tier and still says nothing about this compound.
| Finding | Tier | Distance from use | Study |
|---|---|---|---|
| In adults with obesity or overweight and no diabetes, once-weekly 2.4 mg semaglutide produced a mean 14.9 percent body-weight reduction over 68 weeks, against 2.4 percent with placebo, alongside diet and activity counseling. | rct | not recorded | Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity.New England Journal of Medicine 384(11):989-1002, 2021 |
| In type 2 diabetes, weekly semaglutide at 0.5 or 1.0 mg lowered HbA1c and reduced the combined rate of cardiovascular death, nonfatal heart attack, and nonfatal stroke by 26 percent over two years in a dedicated outcomes trial. | rct | not recorded | Marso SP et al. Semaglutide and Cardiovascular Outcomes in Patients with Type 2 Diabetes.New England Journal of Medicine 375(19):1834-1844, 2016 |
| In people with established cardiovascular disease and a BMI of 27 or higher but no diabetes, 2.4 mg weekly cut major adverse cardiovascular events by 20 percent over a mean of 40 months - the first weight-loss drug shown to do this. | rct | not recorded | Lincoff AM et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes.New England Journal of Medicine 389(24):2221-2232, 2023 |
| Gastrointestinal effects are the dominant side effect and track the escalation phase: at 2.4 mg, nausea affected 44.2 percent of trial participants against 17.4 percent on placebo, and 4.5 percent stopped the drug over gastrointestinal complaints. | rct | not recorded | Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity.New England Journal of Medicine 384(11):989-1002, 2021 |
| The oral tablet form, co-formulated with the absorption enhancer SNAC, lowered HbA1c versus placebo at 3, 7, and 14 mg once daily over 26 weeks in type 2 diabetes. | rct | not recorded | Aroda VR et al. PIONEER 1: Randomized Clinical Trial of the Efficacy and Safety of Oral Semaglutide Monotherapy in Comparison With Placebo in Patients With Type 2 Diabetes.Diabetes Care 42(9):1724-1732, 2019 |
| Sustained GLP-1 receptor stimulation causes thyroid C-cell tumors in rats and mice through calcitonin release and C-cell proliferation. The effect has not been demonstrated in humans, and US semaglutide labels carry it as a boxed warning. | preclinical | not recorded | Bjerre Knudsen L et al. Glucagon-Like Peptide-1 Receptor Agonists Activate Rodent Thyroid C-Cells Causing Calcitonin Release and C-Cell Proliferation.Endocrinology 151(4):1473-1486, 2010 |
| Grey-market users widely report escalating more slowly than the label, holding at the lowest dose that still moves weight, and stretching injection intervals past a week to manage nausea and cost. | anecdotal | not recorded | community reports aggregated from reddit, MESO-Rx, and similar forumsno study |
How did it get here?
- preclinical1982-1993
- GLP-1 is read out of the newly cloned proglucagon gene. By 1987 the peptide is shown to stimulate insulin release, in the perfused rat pancreas and then by infusion in people. The glucose dependence that makes it a plausible drug is pinned down over the following years: in a 1993 infusion study, fasting glucose in poorly controlled type 2 diabetics fell to normal and insulin then eased back toward baseline with the infusion still running. A fragile candidate even so, since native GLP-1 survives about two minutes in blood.
- preclinical2003-2007
- Novo Nordisk chemists set out to stretch their daily analog liraglutide into a weekly drug. Two changes do it: a synthetic amino acid at position 8 blocks the enzyme that destroys GLP-1, and a rebuilt fatty-diacid side chain makes the peptide cling to albumin.
- first-human2008-2016
- Human trials of semaglutide begin. A 12-week dose-finding study spans 0.1 to 1.6 mg weekly; the SUSTAIN phase 3 program then locks in 0.5 and 1.0 mg as the diabetes doses.
- clinical-adoption2017
- FDA approves Ozempic for type 2 diabetes. The tablet form (Rybelsus) follows in 2019, moving roughly 1 percent of a swallowed dose into the blood versus 89 percent injected.
- clinical-adoption2021
- Wegovy approved for chronic weight management at 2.4 mg weekly on the strength of a 14.9 percent mean weight loss in trials. Demand outruns manufacturing almost immediately.
- grey-market2022-2025
- Persistent FDA shortage listings temporarily legalize large-scale compounding, and a parallel research-chemical market sells lyophilized semaglutide vials for home reconstitution. Peptide forums normalize do-it-yourself titration far outside the label, and the vial route outlives the shortage that excused it.
How is it made?
Production happens in three stages.
1. Building the peptide. Semaglutide is a 31-amino-acid analog of human GLP-1. Pharmaceutical manufacture starts biologically: engineered yeast secrete a precursor peptide, which is harvested and finished chemically. Grey-market material comes instead from solid-phase peptide synthesis, the standard route for research peptides - the chain is assembled one amino acid at a time on resin beads, roughly thirty coupling reactions in sequence, each slightly short of perfect. Truncated and deleted chains accumulate with every step and have to be removed later.
2. Installing the two design changes. A synthetic amino acid (aminoisobutyric acid) sits at position 8, exactly where the enzyme DPP-4 would otherwise cut native GLP-1 apart within minutes. A lysine at position 26 carries a short spacer arm ending in an 18-carbon fatty diacid. That side chain is the entire reason the drug works weekly: it binds the peptide tightly to albumin in the blood, and albumin-bound drug is shielded from clearance, turning a half-life of minutes into one of about a week.
3. Purification and fill. The crude peptide is purified by preparative chromatography. Pharmaceutical product is filled as a sterile solution into pens under GMP rules, with every batch tested for identity, potency, sterility, and endotoxins; grey-market product is freeze-dried into vials for reconstitution. The peptide chemistry is well understood. What varies outside regulated manufacturing is everything after it - the purity of the crude material, the sterile fill, and whether the batch was ever tested at all.
Worth knowing
The tablet only works because each dose is pressed together with SNAC, a fatty-acid derivative that locally raises stomach pH and ferries the peptide straight through the stomach wall - absorption happens in the stomach, not the intestine, which is backwards for an oral drug. Even with the trick, about 1 percent of an oral dose reaches the blood, against 89 percent injected, which is why the Rybelsus tablet is dosed at 3 to 14 mg daily while the weekly injections run from the 0.25 mg starting dose to the 2.4 mg Wegovy maintenance dose.
Buckley ST et al. Transcellular stomach absorption of a derivatized glucagon-like peptide-1 receptor agonist.Science Translational Medicine 10(467):eaar7047, 2018
The albumin trick is a Novo Nordisk house method: the same fatty-acylation idea protracts insulin detemir, insulin degludec, and liraglutide. Semaglutide's version, an 18-carbon diacid on a longer spacer, binds albumin so avidly that almost all circulating drug is bound at any moment - the bound fraction is inventory, and only the small free fraction is active and being cleared.
Lau J et al. Discovery of the Once-Weekly Glucagon-Like Peptide-1 (GLP-1) Analogue Semaglutide.Journal of Medicinal Chemistry 58(18):7370-7380, 2015
Reconstitution
Semaglutide ships lyophilized and is mixed before use; the published vial strengths are 5, 2, 10 mg. The water volume you add sets the concentration, not the dose -- the calculator turns a vial size and a water volume into mg/mL, draw volume, and units on an insulin syringe.
Open in the reconstitution calculatorWritten and reviewed by Evan Marlow, developer of DosePlot · Updated 2026-08-27
Not medical advice. DosePlot is an informational tool, not a healthcare provider, and using it creates no provider-patient relationship. Do not start, stop, or change any protocol without the approval of a licensed healthcare professional.
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