Semaglutide
Also known as: Ozempic, Wegovy, Rybelsus, NNC0113-0217
Overview
Clinical Summary
Semaglutide is a long-acting GLP-1 receptor agonist approved for the treatment of type 2 diabetes (Ozempic, Rybelsus) and chronic weight management (Wegovy). It is a modified human GLP-1 analogue with 94% sequence homology to native GLP-1, engineered with an albumin-binding fatty diacid side chain to extend the half-life to approximately 7 days. Semaglutide has been studied in one of the largest clinical development programs for any incretin therapy, including the SUSTAIN series (T2D), STEP series (obesity), and SELECT (cardiovascular outcomes in obesity). Following the SELECT trial, Wegovy became the first anti-obesity medication to receive an FDA indication for cardiovascular risk reduction in patients with overweight or obesity and established cardiovascular disease.
Plain Language Summary
Semaglutide is a prescription medication that mimics a natural gut hormone called GLP-1, which helps control blood sugar and appetite. It is available as a once-weekly injection (Ozempic for diabetes, Wegovy for weight loss) and a daily pill (Rybelsus for diabetes). In clinical trials, people using semaglutide for weight loss lost an average of about 15% of their body weight. It is also the first weight loss medication proven to reduce the risk of heart attacks and strokes in people with obesity and heart disease.
Mechanism of Action
Semaglutide activates GLP-1 receptors on pancreatic beta cells, hypothalamic neurons, and gastrointestinal tract. In the pancreas, GLP-1R activation enhances glucose-dependent insulin secretion and suppresses inappropriate glucagon release. In the central nervous system, semaglutide acts on hypothalamic and brainstem appetite centers (arcuate nucleus, area postrema) to reduce hunger and increase satiety. It also delays gastric emptying, contributing to reduced postprandial glucose excursions and decreased caloric intake. The C-18 fatty diacid modification enables noncovalent albumin binding in the circulation, conferring resistance to DPP-4 degradation and renal clearance, resulting in a half-life of approximately 165 hours suitable for once-weekly dosing.
Evidence Summary
The SUSTAIN program (7 Phase 3 trials) established semaglutide 0.5 and 1.0 mg for T2D, with HbA1c reductions of 1.5 to 1.8% and weight loss of 4 to 6 kg. SUSTAIN-6 (n=3,297) demonstrated a 26% reduction in MACE in T2D patients at high CV risk. The STEP program evaluated semaglutide 2.4 mg for obesity: STEP 1 (n=1,961) showed 14.9% mean weight loss vs 2.4% placebo at 68 weeks. SELECT (n=17,604) demonstrated a 20% reduction in MACE in adults with overweight/obesity and established CV disease without diabetes over a mean 39.8-month follow-up. Limitations include the predominantly White study populations in early trials and the requirement for continued treatment to maintain weight loss, as demonstrated by the weight regain observed in STEP 1 Extension.
Safety Profile
The most common adverse events are gastrointestinal: nausea (20-44%), diarrhea (15-30%), vomiting (5-24%), and constipation (10-24%), which are generally mild to moderate and decrease with continued therapy and slow dose titration. The FDA label carries a boxed warning for thyroid C-cell tumors based on rodent findings. Acute pancreatitis has been reported rarely. SUSTAIN-6 identified a signal for diabetic retinopathy complications in patients with pre-existing retinopathy experiencing rapid glycemic improvement. Acute gallbladder disease (cholelithiasis, cholecystitis) occurs at higher rates with weight loss doses. Suicidal ideation has been included as a monitored event based on post-marketing reports, though a causal relationship has not been established.
Contraindications
- Personal or family history of medullary thyroid carcinoma
- Multiple endocrine neoplasia type 2 (MEN2)
- Known hypersensitivity to semaglutide or any excipients
- Pregnancy (discontinue at least 2 months before planned conception due to long half-life)
- History of serious hypersensitivity reaction to another GLP-1RA
Adverse Events
- Nausea (most common, dose-dependent, typically transient)
- Diarrhea
- Vomiting
- Constipation
- Abdominal pain
- Injection site reactions (subcutaneous formulation)
- Cholelithiasis and cholecystitis (increased with higher doses)
Interactions
- Delays gastric emptying, which may affect absorption of concomitant oral medications; consider monitoring drugs with a narrow therapeutic index
- Increased hypoglycemia risk when combined with insulin or sulfonylureas; dose reduction of these agents may be necessary
- Oral semaglutide (Rybelsus) must be taken on an empty stomach with no more than 4 oz of plain water, at least 30 minutes before food, drink, or other oral medications
- Warfarin: monitor INR when initiating or changing semaglutide dose due to potential delayed absorption effects
Active Safety Signals
All GLP-1RA labels, including semaglutide, carry a boxed warning regarding risk of thyroid C-cell tumors based on rodent studies. Semaglutide caused dose-dependent thyroid C-cell tumors in rats and mice. While relevance to humans is uncertain, semaglutide is contraindicated in patients with a personal or family history of medullary thyroid carcinoma or MEN2.
In the SUSTAIN-6 cardiovascular outcomes trial, semaglutide was associated with a statistically significant increase in diabetic retinopathy complications (HR 1.76, 95% CI 1.11-2.78). This was primarily observed in patients with pre-existing retinopathy who experienced rapid HbA1c reductions. Current labeling advises monitoring in patients with a history of diabetic retinopathy.
Regulatory Notes
Ozempic (semaglutide 0.25, 0.5, 1.0, 2.0 mg injection) was FDA-approved in December 2017 for T2D. Rybelsus (oral semaglutide 3, 7, 14 mg) was approved in September 2019 for T2D. Wegovy (semaglutide 2.4 mg injection) was approved in June 2021 for chronic weight management and received a supplemental indication in March 2024 for cardiovascular risk reduction. All are manufactured by Novo Nordisk. Semaglutide products have experienced significant supply shortages due to high demand, leading to FDA enforcement discretion regarding compounded versions, though the FDA has periodically updated the shortage status.
Monitoring Considerations
Monitor HbA1c, fasting plasma glucose, and body weight at regular intervals. Assess GI tolerability during dose escalation (titrate over 16-20 weeks for the 2.4 mg dose). Monitor for signs and symptoms of pancreatitis. In patients with pre-existing diabetic retinopathy, ophthalmologic evaluation is recommended before initiation and periodically during treatment. Monitor heart rate, as small increases (2-4 bpm) are observed. Assess for cholelithiasis symptoms, particularly in patients with rapid weight loss. Renal function monitoring is advisable, as acute kidney injury has been reported in the setting of severe GI adverse events causing dehydration.
These are general considerations for clinical awareness and do not constitute prescriptive monitoring recommendations for any individual patient.
Stability and Handling Notes
Ozempic/Wegovy pens: store refrigerated at 2 to 8 degrees C prior to first use. After first use, may be stored at room temperature (up to 30 degrees C) or refrigerated for up to 56 days (Ozempic) or 28 days (Wegovy). Protect from light. Do not freeze. Discard if frozen. Rybelsus tablets: store at room temperature in original blister packaging; protect from moisture. The multi-dose pen should be used with disposable needles (not included). Each pen delivers multiple doses.
References
- 1RCT
Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1)
Wilding JPH, Batterham RL, Calanna S, et al. (2021). New England Journal of Medicine
Key findings: Phase 3 RCT in 1,961 adults with overweight or obesity. Semaglutide 2.4 mg weekly achieved 14.9% mean body weight reduction vs 2.4% placebo at 68 weeks. Significant improvements in cardiometabolic risk factors.
Limitations: 68-week duration. Lifestyle intervention in both arms. Predominantly White and female participants.
View source - 2RCT
Semaglutide and Cardiovascular Outcomes in Patients with Type 2 Diabetes (SUSTAIN-6)
Marso SP, Bain SC, Consoli A, et al. (2016). New England Journal of Medicine
Key findings: Cardiovascular outcomes trial in 3,297 patients with T2D at high CV risk. Semaglutide reduced MACE by 26% (HR 0.74, 95% CI 0.58-0.95). Significant reductions in nonfatal stroke and nonfatal MI.
Limitations: Preapproval trial designed for noninferiority. Open-label design for some components. Higher rates of diabetic retinopathy complications with semaglutide.
View source - 3RCT
Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes (SELECT)
Lincoff AM, Brown-Frandsen K, Colhoun HM, et al. (2023). New England Journal of Medicine
Key findings: Landmark RCT of 17,604 adults with overweight/obesity and established CV disease but without diabetes. Semaglutide 2.4 mg reduced MACE by 20% (HR 0.80, 95% CI 0.72-0.90) over a mean 39.8-month follow-up.
Limitations: Population limited to those with established cardiovascular disease. Mean BMI was 33. Predominantly male (72%).
View source - 4FDA label
OZEMPIC (semaglutide) injection Prescribing Information
Novo Nordisk Inc. (2024). FDA
Key findings: Full prescribing information including boxed warning for thyroid C-cell tumors, indications for T2D, dosing, contraindications, warnings, and clinical pharmacology.
Limitations: Label information; not primary research.
View source - 5FDA label
WEGOVY (semaglutide) injection Prescribing Information
Novo Nordisk Inc. (2024). FDA
Key findings: Full prescribing information for the weight management indication. Updated to include cardiovascular risk reduction indication following SELECT trial results.
Limitations: Label information; not primary research.
View source
Last reviewed: 2026-03-24 | Version: 1 | Status: Published