Saxenda vs Wegovy: Which GLP-1 Wins for Weight Loss?
Head-to-head comparison of Saxenda (liraglutide 3mg) vs Wegovy (semaglutide 2.4mg) for weight loss, based on the STEP 8 trial and systematic reviews.
Medically Reviewed
Reviewed by Dr. James Chen, MD, PhD, FACE on March 10, 2026
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Introduction
Saxenda and Wegovy are both FDA-approved injectable GLP-1 receptor agonists for chronic weight management — yet they differ significantly in active drug, dosing frequency, and the magnitude of weight loss they produce. With obesity affecting more than 40% of U.S. adults, choosing between these two medications has become a clinically important decision for patients and prescribers alike.
Both drugs work by activating glucagon-like peptide-1 (GLP-1) receptors in the brain's appetite-regulating centers, slowing gastric emptying and reducing caloric intake. But Saxenda (liraglutide 3.0 mg, Novo Nordisk) requires a daily injection, while Wegovy (semaglutide 2.4 mg, Novo Nordisk) is administered just once per week — and their efficacy data tell a strikingly different story.
The STEP 8 randomized clinical trial provided the first head-to-head evidence: semaglutide produced more than twice the weight loss of liraglutide over 68 weeks, with a comparable GI side effect profile and fewer treatment discontinuations. This article reviews that trial alongside the foundational SCALE and STEP 1 studies to give you a data-driven comparison of both medications.
Drug Profiles at a Glance
| Feature | Saxenda (Liraglutide) | Wegovy (Semaglutide) |
|---|---|---|
| Drug class | GLP-1 receptor agonist | GLP-1 receptor agonist |
| FDA approval (obesity) | December 2014 | June 2021 |
| Approved dose | 3.0 mg/day subcutaneous | 2.4 mg/week subcutaneous |
| Injection frequency | Once daily | Once weekly |
| Half-life | ~13 hours | ~7 days |
| Average weight loss (trial) | −8.0% (SCALE) | −14.9% (STEP 1) |
| Starting dose | 0.6 mg/day, titrate over 5 weeks | 0.25 mg/week, titrate over 16 weeks |
The longer half-life of semaglutide — approximately 7 days versus 13 hours for liraglutide — explains the once-weekly versus once-daily dosing. Both require subcutaneous injections via a pre-filled pen, and both are used alongside diet and physical activity counseling.
Saxenda: The SCALE Obesity Trial
The foundational evidence for Saxenda comes from the SCALE (Satiety and Clinical Adiposity — Liraglutide Evidence) Obesity and Prediabetes trial, a 56-week phase 3 RCT published in The New England Journal of Medicine in 2015.
Evidence: "3.0 mg of once-daily subcutaneous liraglutide was associated with clinically meaningful weight loss in overweight or obese patients, with concurrent reductions in glycemic variables and multiple cardiometabolic risk factors." — Pi-Sunyer X, et al. N Engl J Med. 2015;373(1):11-22. DOI: 10.1056/NEJMoa1411892
The trial enrolled 3,731 adults with a BMI ≥30 or ≥27 with a weight-related comorbidity. At 56 weeks:
- Mean weight loss: −8.4 kg (−8.0%) with liraglutide vs −2.8 kg with placebo
- 63% of liraglutide patients achieved ≥5% weight loss (vs 27% placebo)
- 33% achieved ≥10% weight loss (vs 10% placebo)
These results established liraglutide as a meaningful weight management tool — a meaningful advance over prior pharmacotherapy options at the time of its approval.
Wegovy: The STEP 1 Trial
Wegovy's approval rests on the STEP (Semaglutide Treatment Effect in People with Obesity) program. STEP 1, published in NEJM in 2021, is the landmark efficacy trial.
Evidence: "The mean change in body weight from baseline to week 68 was −14.9% in the semaglutide group as compared with −2.4% with placebo, for an estimated treatment difference of −12.4 percentage points." — Wilding JPH, et al. N Engl J Med. 2021;384(11):989-1002. DOI: 10.1056/NEJMoa2032183
STEP 1 enrolled 1,961 adults without diabetes. At 68 weeks:
- Mean weight loss: −14.9% (−15.3 kg) with semaglutide vs −2.4% with placebo
- 86% of semaglutide patients achieved ≥5% weight loss
- 69% achieved ≥10% weight loss
- 50% achieved ≥15% weight loss
The scale of weight loss was unprecedented for a non-surgical intervention at the time and triggered massive clinical interest in once-weekly semaglutide as a weight management option.
Head-to-Head: The STEP 8 Trial
While the SCALE and STEP 1 trials used placebo controls, the STEP 8 trial directly compared both active drugs under identical conditions — making it the gold-standard evidence for the Saxenda vs Wegovy question.
Evidence: "Mean body weight change from baseline to 68 weeks was −15.8% with semaglutide versus −6.4% with liraglutide (difference −9.4 percentage points; 95% CI, −11.8 to −7.0; P<0.001)." — Wadden TA, et al. JAMA. 2022;327(2):138-150. DOI: 10.1001/jama.2021.23619
The trial randomized 338 adults with overweight or obesity (without diabetes) across 19 U.S. sites to 68 weeks of once-weekly semaglutide 2.4 mg, once-daily liraglutide 3.0 mg, or placebo — all combined with behavioral counseling for diet and exercise.
STEP 8 Weight Loss Results
| Endpoint | Semaglutide 2.4 mg | Liraglutide 3.0 mg | Placebo |
|---|---|---|---|
| Mean weight change | −15.8% | −6.4% | −2.6% |
| Mean kg lost | −15.3 kg | −6.8 kg | −2.7 kg |
| ≥5% weight loss | 90.0% | 67.3% | 45.2% |
| ≥10% weight loss | 75.6% | 30.8% | 16.1% |
| ≥15% weight loss | 55.6% | 12.0% | 4.0% |
| ≥20% weight loss | 38.5% | 6.0% | 1.3% |
At every threshold, semaglutide significantly outperformed liraglutide. The gap widens at higher weight loss targets: roughly 6× more semaglutide patients than liraglutide patients achieved ≥20% weight loss.
Why Does Semaglutide Produce Greater Weight Loss?
The molecular differences between the two drugs help explain the efficacy gap. Semaglutide was engineered with a fatty acid chain that binds albumin more tightly, resulting in a half-life of approximately 7 days. This sustained receptor occupancy produces more consistent appetite suppression compared to liraglutide's daily peak-and-trough pattern. Additionally, semaglutide has demonstrated stronger central nervous system effects on appetite and food reward behavior in neuroimaging studies.
Side Effects: How Do They Compare?
Both drugs share the same GLP-1 receptor agonist side effect class — primarily gastrointestinal — and the STEP 8 trial quantified these differences directly.
Evidence: "GI adverse events were reported by 84.1% of participants receiving semaglutide and 82.7% of those on liraglutide. Fewer participants stopped treatment due to adverse events with semaglutide (3.2%) than liraglutide (12.6%)." — Wadden TA, et al. JAMA. 2022;327(2):138-150. DOI: 10.1001/jama.2021.23619
The raw GI event rates were nearly identical — approximately 84% for both. However, the critical difference is in treatment discontinuation due to side effects: 3.2% for semaglutide versus 12.6% for liraglutide. This suggests that while both drugs trigger similar GI symptoms, semaglutide patients tolerate them better and stay on treatment longer.
Common Side Effects (Both Drugs)
| Side Effect | Semaglutide (STEP 8) | Liraglutide (STEP 8) |
|---|---|---|
| Nausea | ~57% | ~56% |
| Diarrhea | ~35% | ~29% |
| Constipation | ~27% | ~25% |
| Vomiting | ~25% | ~28% |
| Stopped treatment (AEs) | 3.2% | 12.6% |
Both drugs carry FDA warnings for risk of thyroid C-cell tumors (based on rodent data), pancreatitis, and gallbladder disease. Neither is recommended during pregnancy. These contraindications are class effects and apply equally to both medications.
Systematic Review: Confirming the Efficacy Gap
A 2022 systematic review and network meta-analysis examined 23 randomized controlled trials involving 11,545 patients across multiple GLP-1 receptor agonists and weight management medications.
Evidence: "Among pharmacological treatments for obesity, semaglutide 2.4 mg achieved the greatest weight loss (−12.47 kg), followed by liraglutide 3.0 mg (−5.24 kg), both significantly superior to placebo." — Shi Q, et al. Front Endocrinol. 2022;13:1043499. PubMed
This independent, pooled analysis confirms the efficacy hierarchy seen in STEP 8: semaglutide achieves approximately 2.4× greater absolute weight loss than liraglutide in real-world trial populations.
Cost and Access Considerations
Both Saxenda and Wegovy are manufactured by Novo Nordisk, and both carry list prices exceeding $1,000/month without insurance. However, insurance coverage differs significantly:
- Saxenda was approved in 2014 and has more established formulary placement at many commercial plans
- Wegovy was approved in 2021 and faced widespread coverage denials before increasing adoption; availability has been limited by periodic supply constraints
Both medications require a BMI ≥30, or ≥27 with at least one weight-related comorbidity, for prescription under label. Some insurers apply step-therapy requirements, meaning liraglutide may be required before semaglutide coverage is authorized.
For patients exploring coverage options, our guide to insurance coverage for weight loss drugs covers strategies for navigating prior authorization.
Which Should You Choose?
The clinical evidence strongly favors Wegovy (semaglutide 2.4 mg) when weight loss efficacy is the primary consideration. The STEP 8 trial showed semaglutide producing 2.5× greater weight loss than liraglutide with better tolerability (fewer treatment discontinuations) and only once-weekly dosing versus daily injections.
That said, Saxenda may be appropriate in specific scenarios:
- Insurance requires prior liraglutide trial before semaglutide approval
- Patient has a documented intolerance to semaglutide
- Cost or supply constraints make liraglutide more accessible
- Patient prefers more frequent dosing for behavioral reassurance (less common)
The decision should always involve a clinician who can account for a patient's full medical history, comorbidities, prior medication history, and insurance situation. For patients currently on Saxenda who want to know how to transition to Wegovy, the Wegovy dosing schedule article outlines the titration protocol and what to expect in the first weeks of treatment.
Key Takeaways
- Wegovy (semaglutide 2.4 mg once weekly) produces approximately 2.5× greater weight loss than Saxenda (liraglutide 3.0 mg once daily) based on the STEP 8 head-to-head trial (−15.8% vs −6.4% at 68 weeks)
- Both drugs cause similar rates of GI side effects, but far fewer patients discontinue semaglutide due to adverse events (3.2% vs 12.6%)
- Once-weekly dosing with Wegovy offers a convenience advantage over Saxenda's daily injection requirement
- Both require a BMI ≥30 (or ≥27 with comorbidity), lifestyle counseling, and a physician's prescription
- Insurance formularies and cost may influence which drug is accessible for a given patient
References
Pi-Sunyer X, et al. A Randomized, Controlled Trial of 3.0 mg of Liraglutide in Weight Management. N Engl J Med. 2015;373(1):11-22. DOI: 10.1056/NEJMoa1411892
Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021;384(11):989-1002. DOI: 10.1056/NEJMoa2032183
Wadden TA, et al. Effect of Weekly Subcutaneous Semaglutide vs Daily Liraglutide on Body Weight in Adults With Overweight or Obesity Without Diabetes: The STEP 8 Randomized Clinical Trial. JAMA. 2022;327(2):138-150. DOI: 10.1001/jama.2021.23619
Shi Q, et al. Efficacy and Safety of Liraglutide and Semaglutide on Weight Loss in People with Obesity or Overweight: A Systematic Review. Front Endocrinol. 2022;13:1043499. PubMed
Wadden TA, et al. Effect of Weekly Subcutaneous Semaglutide vs Daily Liraglutide on Body Weight — STEP 8. JAMA. 2022. PubMed
Last updated: 2026-03-10 Medical review: Dr. James Chen, MD, PhD, FACE
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Written By
Dr. Sarah Mitchell
Medical Director, MD, FACP
Dr. Sarah Mitchell is a board-certified internist specializing in metabolic medicine and weight management. With over 15 years of clinical experience, she has helped thousands of patients achieve sustainable weight loss through evidence-based approaches.
Medical Reviewer
Dr. James Chen
Endocrinologist, MD, PhD, FACE
Dr. James Chen is a fellowship-trained endocrinologist with expertise in diabetes, metabolism, and hormone-related weight disorders. His research on GLP-1 receptor agonists has been published in leading medical journals.
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