Semaglutide

Semaglutide is best known as the medicine behind Ozempic and Wegovy — a GLP-1 receptor agonist that copies a natural gut hormone involved in fullness and blood-sugar control. It's an FDA-approved prescription medicine, sold as Ozempic and Rybelsus for type 2 diabetes and Wegovy for chronic weight management, given as a weekly injection under the skin or, for Rybelsus, a daily tablet.

Semaglutide (Ozempic, Wegovy) is a GLP-1 injection with the deepest evidence base in its class, FDA-approved for type 2 diabetes and weight management. In large trials it lowered blood sugar (HbA1c) and, at higher doses, produced average weight loss of about 15% over 68 weeks versus about 2% on placebo. A separate outcomes trial reported a 20% reduction in major heart events in adults with overweight or obesity and existing heart disease. In the ESSENCE trial in fatty-liver disease (MASH), more participants had resolution of steatohepatitis without worsening fibrosis than on placebo (62.9% vs 34.3%), and in the FLOW trial (type 2 diabetes with chronic kidney disease) it reduced a composite of kidney and cardiovascular events (hazard ratio 0.76). It has the longest safety record of the GLP-1 family. The research attributes these weight and blood-sugar changes largely to reduced appetite and food intake (greater satiety via the gut-hormone pathway these agents act on), an appetite and energy-intake mechanism measured across the trials.

FDA approved across multiple brands and indications — Ozempic (type 2 diabetes, 2017; cardiovascular risk reduction, 2020; chronic kidney disease progression, Jan 2025 on the FLOW trial); Wegovy (chronic weight management, 2021; cardiovascular risk reduction, 2024 on the SELECT trial; noncirrhotic MASH with moderate-to-advanced fibrosis, accelerated approval Aug 2025 on the ESSENCE trial); Rybelsus (oral, type 2 diabetes, 2019; cardiovascular risk reduction, Oct 2025 on the SOUL trial). A once-daily oral semaglutide formulation (oral Wegovy) was approved for chronic weight management and cardiovascular risk reduction in Dec 2025. A peripheral artery disease indication (STRIDE trial) has been filed with FDA and remains pending decision.

Semaglutide is a prescription-only medication. VialWise is a research and educational reference, not medical advice — talk to a licensed clinician before considering any compound.

⚠️ For research and educational purposes only. Semaglutide is FDA approved under several brand names (Ozempic, Wegovy, Rybelsus) for specific indications. Information in this entry is informational, not medical advice. Always confirm dose calculations with the in-app calculator and consult appropriate professional guidance before any protocol decisions.

⚠️ Precision matters at low doses. Small dosing errors that look trivial in absolute terms can be significant in percentage terms when starting doses are small. A one-unit mis-draw at a 5-unit dose is a 20% error; the same one-unit error at a 50-unit dose is only 2%. This applies most acutely to semaglutide's starting dose, which lands depending on reconstitution. Always verify draws against the in-app calculator and double-check the unit count on the syringe before injecting.

Semaglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist developed by Novo Nordisk and marketed under three brand names depending on indication and route: Ozempic (subcutaneous, type 2 diabetes), Wegovy (subcutaneous, chronic weight management), and Rybelsus (oral tablet, type 2 diabetes). Its approved indications have expanded well beyond glucose and weight control. Ozempic added cardiovascular risk reduction (2020) and, on the basis of the phase-3 FLOW trial, reduction of chronic-kidney-disease progression, kidney failure and cardiovascular death in type 2 diabetes with CKD (FDA approved Jan 2025).[¹⁰] Wegovy added cardiovascular risk reduction (2024, on the SELECT trial) and, on the basis of the phase-3 ESSENCE trial, treatment of noncirrhotic MASH with moderate-to-advanced fibrosis (accelerated approval Aug 2025 — the first GLP-1 approved for MASH).[⁹] Rybelsus added cardiovascular risk reduction in high-risk type 2 diabetes on the basis of the phase-3 SOUL trial (FDA approved Oct 2025 — the first oral GLP-1 with a CV indication).[¹¹] A once-daily oral semaglutide formulation (oral Wegovy) was approved for chronic weight management and cardiovascular risk reduction in Dec 2025. A peripheral-artery-disease indication, studied in the phase-3b STRIDE trial, has been filed but is not yet FDA approved as of July 2026.[¹²] (Note: two phase-3 trials of oral semaglutide in early Alzheimer's disease, EVOKE and EVOKE+, showed no cognitive benefit and were discontinued — semaglutide has no established role in Alzheimer's disease or other neurodegenerative conditions.[¹³]) It is the most extensively studied incretin therapy currently approved, with millions of patient-years of post-marketing data and several large cardiovascular outcomes trials supporting its safety and efficacy in defined populations.

Mechanistically, semaglutide is a single-receptor agonist (GLP-1 only) — distinct from the dual agonist tirzepatide (GLP-1/GIP) and the triple agonist retatrutide (GLP-1/GIP/glucagon). GLP-1 receptor activation drives glucose-dependent insulin secretion, suppresses glucagon, slows gastric emptying, and reduces appetite through central pathways acting on the arcuate nucleus of the hypothalamus. The 39-amino-acid peptide is conjugated to a C18 fatty di-acid moiety for albumin binding, which is the structural basis for once-weekly subcutaneous dosing;[⁵] the human half-life of approximately 165 hours (~7 days) is the value reported in the FDA prescribing information.[⁶]

The pivotal obesity trial (STEP-1; Wilding et al., NEJM 2021; n=1,961) reported a least-squares mean weight reduction of −14.9% with semaglutide weekly versus −2.4% with placebo at 68 weeks, when combined with lifestyle intervention.[¹] In type 2 diabetes, trials across the SUSTAIN program reported HbA1c reductions of approximately 1.0–1.8 percentage points with weight reductions of several kilograms; the specific trial cited here — SUSTAIN-6 — was a cardiovascular-safety trial at the and weekly doses (the weekly Ozempic dose derives from the later sustain forte trial, not cited).[³] The SELECT cardiovascular outcomes trial (Lincoff et al., NEJM 2023; n=17,604) reported a 20% reduction in major adverse cardiovascular events in adults with overweight or obesity and pre-existing cardiovascular disease but without diabetes — the first GLP-1 trial to show CV benefit independent of diabetes status.[²]

Semaglutide differs from retatrutide and tirzepatide in three respects worth flagging for researchers comparing the GLP-1 family: (1) lower absolute weight loss in head-to-head and cross-trial comparisons (~15% vs ~21% for tirzepatide vs ~25–28% for retatrutide at maximum doses, the retatrutide figure reflecting its phase-3 read-out); (2) the longest published safety record by a wide margin; and (3) the only GLP-1 with established cardiovascular outcomes data in a non-diabetic population.

Commonly reported

• Nausea — most common dose-limiting side effect, typically dose-dependent and most pronounced during titration steps
• Vomiting
• Diarrhea
• Constipation
• Decreased appetite (often reported as a benefit; extreme cases warrant dose reduction)
• Fatigue
• Injection site reactions
• Anhedonia and mood flattening (reported across the incretin class)
• Headache
• Hypoglycemia (uncommon as monotherapy; more common when combined with insulin or sulfonylureas in T2D contexts)

Serious

• Severe persistent vomiting or signs of dehydration
• Acute pancreatitis symptoms (severe abdominal pain radiating to back)
• Gallbladder symptoms (right upper quadrant pain, jaundice) — gallstones and cholecystitis reported at elevated rates in semaglutide trials
• Acute kidney injury (typically secondary to dehydration from GI side effects)
• Diabetic retinopathy worsening (observed in T2D contexts, especially when adding semaglutide on top of existing diabetes therapy)
• Suicidal ideation or new-onset mood changes (under regulatory review across the incretin class as of 2024–2025)

Personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN2) — FDA-mandated boxed warning across the incretin class, based on rodent thyroid C-cell tumor findings; human relevance is debated but the warning is legally binding for prescribers in the US

History of pancreatitis

Severe gastrointestinal disease (gastroparesis especially — semaglutide further slows gastric emptying)

Severe renal impairment (limited data; dehydration risk amplifies)

Concurrent use of other GLP-1, GIP, or glucagon receptor agonists

Pregnancy and lactation: not recommended. Animal studies showed reproductive toxicity; the Wegovy and Ozempic labels recommend discontinuation at least 2 months before a planned pregnancy due to the long half-life

GLP-1 receptor agonist

A compound that switches on the GLP-1 receptor, the same target a natural gut hormone uses to signal fullness and help regulate blood sugar.

Subcutaneous

An injection into the fatty layer just under the skin, rather than into a muscle or vein.

Half-life

Roughly how long the body takes to clear half of a dose. A long half-life is why some compounds can be taken only once a week.

Titration

Starting at a low dose and increasing it gradually.

1. Wilding JPH, Batterham RL, Calanna S, Davies M, Van Gaal LF, Lingvay I, McGowan BM, Rosenstock J, Tran MTD, Wadden TA, Wharton S, Yokote K, Zeuthen N, Kushner RF, for the STEP 1 Study Group. (2021). Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine, 384(11):989–1002.(PMID 33567185 · NCT03548935)
2. Lincoff AM, Brown-Frandsen K, Colhoun HM, Deanfield J, Emerson SS, Esbjerg S, Hardt-Lindberg S, Hovingh GK, Kahn SE, Kushner RF, Lingvay I, Oral TK, Michelsen MM, Plutzky J, Tornøe CW, Ryan DH, for the SELECT Trial Investigators. (2023). Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes. New England Journal of Medicine, 389(24):2221–2232.(PMID 37952131 · NCT03574597)
3. Marso SP, Bain SC, Consoli A, et al., for the SUSTAIN-6 Investigators. (2016). Semaglutide and Cardiovascular Outcomes in Patients with Type 2 Diabetes. New England Journal of Medicine, 375(19):1834–1844.(PMID 27633186 · NCT01720446)
4. Aroda VR, Rosenstock J, Terauchi Y, et al., for the PIONEER 1 Investigators. (2019). 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.(PMID 31186300 · NCT02906930)
5. Lau J, Bloch P, Schäffer L, Pettersson I, Spetzler J, Kofoed J, Madsen K, Knudsen LB, McGuire J, Steensgaard DB, Strauss HM, Gram DX, Knudsen SM, Nielsen FS, Thygesen P, Reedtz-Runge S, Kruse T. (2015). Discovery of the Once-Weekly Glucagon-Like Peptide-1 (GLP-1) Analogue Semaglutide. Journal of Medicinal Chemistry, 58(18):7370–7380.(PMID 26308095)
6. Novo Nordisk. Ozempic (semaglutide) injection prescribing information. US Food and Drug Administration. NDA 209637, current label combining SUPPL-35 and SUPPL-37, both approved 2025-10-14.
7. McCrimmon RJ, Catarig AM, Frias JP, Lausvig NL, le Roux CW, Thielke D, Lingvay I. (2020). Effects of once-weekly semaglutide vs once-daily canagliflozin on body composition in type 2 diabetes: a substudy of the SUSTAIN 8 randomised controlled clinical trial. Diabetologia, 63(3):473–485.(PMID 31897524 · NCT03136484)
8. Novo Nordisk. Wegovy (semaglutide) injection prescribing information. US Food and Drug Administration. NDA 215256, current label SUPPL-29 (Efficacy-New Dosing Regimen) approved 2026-03-19.

• CJC-1295 / Ipamorelin Blend — discussed together in this entry's stacks section
• BPC-157 / TB-500 Blend — discussed together in this entry's stacks section
• Tesamorelin — discussed together in this entry's stacks section
• Amycretin — same mechanism class
• CagriSema — same mechanism class
• Dulaglutide — same mechanism class