Short answer: Liraglutide (Saxenda for weight, Victoza for diabetes) is a GLP-1 drug injected daily, with a half-life of about 13 hours.1 Tirzepatide (Zepbound, Mounjaro) acts on GIP and GLP-1 receptors and is injected weekly, with a half-life of about 5 days.2 We found no trial comparing them head to head for weight. Liraglutide is available as a generic.3
Because there is no head-to-head trial, this page sticks to what each label says. Numbers from each drug's own trials are not comparable with each other: the people, lengths and designs differ.
| Liraglutide (Saxenda, Victoza) | Tirzepatide (Zepbound, Mounjaro) | |
|---|---|---|
| Mechanism | GLP-1 receptor agonist1 | GIP and GLP-1 receptor agonist2 |
| Approved uses | Saxenda: weight, adults and ages 12 and up over 60 kg with obesity. Victoza: type 2 diabetes (ages 10 and up) and heart risk with heart disease14 | Zepbound: weight and sleep apnea with obesity, adults. Mounjaro: type 2 diabetes (ages 10 and up) and heart risk25 |
| How often | Once daily1 | Once weekly2 |
| Weight dosing | Saxenda: 0.6 mg daily, up 0.6 mg each week to 3 mg1 | Zepbound: 2.5 mg weekly for 4 weeks, then up by 2.5 mg every 4 or more weeks; maintenance 5, 10 or 15 mg2 |
| Stop rule | Saxenda: stop if under 4% weight loss after 16 weeks (adults)1 | No set cut-off; pick the maintenance dose by response and tolerability2 |
| Half-life | about 13 hours (label: about 13 hours)1 | about 5 days (Zepbound label: about 5 to 6 days)2 |
| Time to peak | 11 hours (Saxenda); 8 to 12 hours (Victoza)14 | Median 24 hours (8 to 72)2 |
| Missed dose | Saxenda: skip it; if more than 3 days missed, restart at 0.6 mg1 | Take within 4 days; otherwise skip2 |
| Devices | Multi-dose pen, 6 mg/mL1 | Single-dose pens and vials, 4-dose vials and KwikPens2 |
| Generic | Yes: generics referencing Victoza (2024) and Saxenda (2025)3 | No |
Not in a randomized trial for weight. We searched PubMed and ClinicalTrials.gov in October 2026 and found no head-to-head trial of liraglutide against tirzepatide. The closest are trials that compared each drug with semaglutide: liraglutide in Semaglutide vs liraglutide: what is the difference? (STEP 8) and tirzepatide in Semaglutide vs tirzepatide: what did the head-to-head trial show? (SURMOUNT-5). Chaining those together does not give a fair liraglutide vs tirzepatide answer.
Their own approval trials also differ. Saxenda's weight trials ran 56 weeks, with the dose raised to 3 mg over 4 weeks.1 Zepbound's ran 72 weeks, with a dose increase of up to 20 weeks.2
With a half-life of about 13 hours, liraglutide is mostly gone within a few days, so it needs a daily shot. A missed Saxenda dose is skipped, and after more than 3 missed days the label restarts the dose climb at 0.6 mg.1 Tirzepatide's half-life of about 5 days lets one shot cover the week, and a missed dose can be taken up to 4 days late.2
Tirzepatide levels also take longer to settle. Steady levels arrive after about 4 weeks of weekly shots,2 and the drug takes longer to clear after the last dose.
Each molecule has a weight brand and a diabetes brand. For weight: Saxenda includes teens 12 and up who weigh more than 60 kg, while Zepbound is adults only but adds obstructive sleep apnea.12 For diabetes: both Victoza and Mounjaro include children 10 and up and carry a heart risk indication.45