Saxenda and Zepbound have never been tested against each other, and the gap between them on their own labels is wide. Saxenda's main trial reports 7.4% average weight loss at 56 weeks; Zepbound's reports 15% to 21% at 72 weeks. The gap is not a clean measure of the drugs, because the trials ran for different lengths and a decade apart. The labels also differ on who can use each drug: Saxenda is approved from age 12, Zepbound only for adults, and only Zepbound also treats sleep apnoea. Saxenda is a daily injection; Zepbound is weekly.
This page reads the two US labels on DailyMed, opened on 2 November 2026: Saxenda (liraglutide, Novo Nordisk, effective 25 February 2026) and Zepbound (tirzepatide, Eli Lilly, effective 28 August 2026). It does not recommend either. Each drug has its own page here: Saxenda and what Zepbound is.
The two drugs side by side
| Saxenda | Zepbound | |
|---|---|---|
| Molecule | liraglutide | tirzepatide |
| What it acts on | GLP-1 receptor | GIP and GLP-1 receptors |
| First approved for weight | December 2014 | November 2023 |
| How often | once a day, injection | once a week, injection |
| Weight indication | adults with obesity, or overweight with a weight-related condition; children 12 and older with obesity and body weight over 60 kg | adults with obesity, or overweight with a weight-related condition |
| Other indication | none | moderate to severe obstructive sleep apnoea in adults with obesity |
| Generic copies | three rated equivalent (Orange Book code AP2) | none |
Both labels say the drug is used "in combination with a reduced calorie diet and increased physical activity", and both say it should not be combined with another GLP-1 receptor agonist. Zepbound's sleep apnoea data are on GLP-1s and sleep apnoea.
Weight loss in each drug's own trials
Every row below is a separate placebo-controlled trial printed in the drug's own label. They are placed side by side because people search for them side by side. They are not a head-to-head comparison.
| Trial (label) | Who | Length | Drug arm(s) | Placebo | Difference from placebo |
|---|---|---|---|---|---|
| Saxenda Study 1 | 3,731 adults, obesity or overweight + comorbidity, no diabetes; mean 106 kg | 56 weeks | −7.4% | −3.0% | −4.5 points |
| Saxenda Study 2 | 635 adults with type 2 diabetes; mean 106 kg | 56 weeks | −5.4% | −1.7% | −3.7 points |
| Saxenda Study 3 | 422 adults who first lost ≥5% on a low-calorie diet | 56 weeks after the run-in | −4.9% | +0.3% | −5.2 points |
| Zepbound Study 1 | 2,539 adults, obesity or overweight + comorbidity, no diabetes; mean 103–106 kg | 72 weeks | 5 mg −15.0% · 10 mg −19.5% · 15 mg −20.9% | −3.1% | −11.9 / −16.4 / −17.8 points |
| Zepbound Study 2 | 938 adults with type 2 diabetes; mean 100–102 kg | 72 weeks | 10 mg −12.8% · 15 mg −14.7% | −3.2% | −9.6 / −11.6 points |
Doses are the trial arms, named so the figures can be read; they are not a recommendation. On the share of people reaching a 5% loss, Saxenda's Study 1 reports 62.3% against 34.4% on placebo; its Study 3 figure is from randomisation, after the diet run-in, which the label itself says "may not reflect those expected in the general population".
Why the columns cannot simply be subtracted. Zepbound's trials ran 16 weeks longer. Both used a similar lifestyle programme (about a 500-calorie daily deficit and at least 150 minutes of activity a week), but they were run years apart with different methods for handling missing data, which each label describes. Within each label, the comparison with placebo is the reliable number; between labels, only the direction is. For the semaglutide and liraglutide pair there is a head-to-head trial, reported on semaglutide vs liraglutide; for this pair there is none.
Side effects in each label
| Adverse reaction | Saxenda (adults, N=3,384) | Placebo | Zepbound 5 / 10 / 15 mg | Placebo |
|---|---|---|---|---|
| Nausea | 39.3% | 13.8% | 25 / 29 / 28% | 8% |
| Diarrhoea | 20.9% | 9.9% | 19 / 21 / 23% | 8% |
| Constipation | 19.4% | 8.5% | 17 / 14 / 11% | 5% |
| Vomiting | 15.7% | 3.9% | 8 / 11 / 13% | 2% |
| Dizziness | 6.9% | 5.0% | 4 / 5 / 4% | 2% |
| Fatigue | 7.5% | 4.6% | 5 / 6 / 7% | 3% |
| Stopped for an adverse reaction | 9.8% | 4.3% | 4.8 / 6.3 / 6.7% | 3.4% |
Sources: Saxenda label Table 2 (five placebo-controlled adult trials, up to 56 weeks); Zepbound label Table 1 and section 6.1 (pool of Studies 1 and 2, 72 weeks). Zepbound's fatigue row pools asthenia, fatigue, lethargy and malaise; its diarrhoea row includes frequent bowel movements. The Saxenda label adds that the most common reasons for stopping were nausea (2.9%), vomiting (1.7%) and diarrhoea (1.4%). Both labels state that rates from different trials "cannot be directly compared". What is clear from both is that the older, daily drug does not show lower gastrointestinal rates. Each drug's full list is on Zepbound side effects and GLP-1 side effects.
Daily versus weekly
Saxenda is injected every day; its label steps the dose up weekly over four weeks to its 3 mg maintenance dose. Zepbound is injected once a week, stepping up every four weeks or more. Neither label reports a trial of adherence by dosing frequency, so this page does not claim one schedule is easier to keep to. The step-up schedules themselves are compared on GLP-1 titration schedules.
Cost and generics
Saxenda is the only weight-management GLP-1 with generic copies. FDA's Orange Book rates liraglutide from Teva (approved August 2025), Biocon and Orbicular (both February 2026) as therapeutically equivalent to Saxenda, code AP2; the detail, and Novo Nordisk's notice that a Saxenda pack will be discontinued in January 2027, are on the Saxenda page. Tirzepatide has no approved generic; the patent record is on when tirzepatide will go generic.
Prices change often, so they are kept on dated pages rather than repeated here: Zepbound cost and the GLP-1 cost hub, which lists each self-pay route with the date it was read.
What this comparison cannot answer
- Which drug works better for one person. That depends on their health record, other medicines and what is covered; it is a prescriber's decision.
- Long-term outcomes head to head. Neither label reports a trial of one drug against the other, at any length.
- Teenagers on Zepbound. Zepbound's weight indication does not cover them, so its label has no adolescent weight data to set against Saxenda's.
Sources
- Saxenda (liraglutide) US prescribing information, effective 25 February 2026: sections 1, 6.1 (Table 2), 14.1 (Table 4). Read on DailyMed, 2 November 2026.
- Zepbound (tirzepatide) US prescribing information, effective 28 August 2026: sections 1, 6.1 (Table 1), 14.1 (Table 2). Read on DailyMed, 2 November 2026.
- FDA Orange Book liraglutide entries as reported on this site's Saxenda page (product file of 11 September 2026).