Saxenda vs Wegovy vs Mounjaro — the full GLP-1 ladder compared

The three medications, in one paragraph each

Saxenda (liraglutide). The first generation: a once-daily injection of liraglutide, a GLP-1 receptor agonist. MHRA-licensed for adults with BMI ≥30 (or ≥27 with comorbidity) and — uniquely — for adolescents aged 12–17 with obesity in specific scenarios. Average weight loss in pivotal trials around 6–8% over 56 weeks. Now considered the gentler, lower-efficacy option, generally chosen when weekly options aren't suitable.

Wegovy (semaglutide). The second generation: once-weekly semaglutide at higher doses than the diabetes-licensed Ozempic. GLP-1 receptor agonist. MHRA-licensed for chronic weight management in adults meeting BMI criteria. Pivotal trial weight loss around 15% over 68 weeks at full dose. The 'modern default' option from 2022 onwards. For the full explainer see our Wegovy guide.

Mounjaro (tirzepatide). The third generation: once-weekly tirzepatide, a dual GIP/GLP-1 receptor agonist. MHRA-licensed for chronic weight management and for type 2 diabetes. Pivotal trial weight loss around 20–22% over 72 weeks at the highest dose. The best-evidenced largest-effect option as of 2026. For the full explainer see our Mounjaro guide. For a deep dive on Mounjaro vs Wegovy specifically, see Mounjaro vs Wegovy.

How they actually work

All three target the GLP-1 receptor system — the gut hormone signalling pathway involved in appetite, satiety, gastric emptying, and insulin response. Differences:

• Liraglutide is a GLP-1 receptor agonist with about a 13-hour half-life. Daily dosing maintains the signal.
• Semaglutide is a long-acting GLP-1 receptor agonist with about a 7-day half-life. Weekly dosing maintains the signal.
• Tirzepatide is a long-acting dual GIP and GLP-1 receptor agonist (a 'twincretin') with about a 5-day half-life. Weekly dosing. The dual mechanism appears to amplify weight reduction and may modulate the GI side effect intensity.

The progression from daily to weekly to dual-agonist isn't just convenience — it reflects genuine increases in average efficacy at each step.

Dosing schedules

Saxenda (liraglutide): daily subcutaneous injection. Dose-titrated weekly: 0.6 → 1.2 → 1.8 → 2.4 → 3.0 mg. Maintenance dose: 3.0 mg daily.

Wegovy (semaglutide): weekly subcutaneous injection. Dose-titrated every 4 weeks: 0.25 → 0.5 → 1.0 → 1.7 → 2.4 mg. Maintenance dose: 2.4 mg weekly.

Mounjaro (tirzepatide): weekly subcutaneous injection. Dose-titrated every 4 weeks: 2.5 → 5 → 7.5 → 10 → 12.5 → 15 mg. Maintenance dose: 5 mg, 10 mg, or 15 mg weekly depending on response and tolerability.

Practical impact: Saxenda needs daily injection discipline; Wegovy and Mounjaro are weekly with significantly less day-to-day burden. For patients with needle anxiety, the once-weekly schedule is much easier to sustain.

The efficacy data, fairly

From pivotal trials in adults with obesity:

• Liraglutide (SCALE Obesity and Prediabetes trial): ~5–8% average weight loss vs placebo over 56 weeks at 3.0 mg/day.
• Semaglutide (STEP-1 trial): ~14.9% average weight loss vs placebo over 68 weeks at 2.4 mg weekly.
• Tirzepatide (SURMOUNT-1 trial): ~20.9% (at 15 mg) and ~19.5% (at 10 mg) average weight loss vs placebo over 72 weeks.
• Head-to-head (SURMOUNT-5): tirzepatide vs semaglutide — tirzepatide produced larger weight loss across all measured endpoints.

Averages aren't promises. Individual response on any of the three varies enormously based on starting weight, dose tolerance, lifestyle scaffolding, and consistency. Some patients on Saxenda lose 15%; some on Mounjaro lose 8%. The averages tell you what the molecule does at population level.

Side effect profiles

The GLP-1-family profile is shared across all three: nausea (especially after dose increases and fatty meals), mild constipation, occasional reflux, reduced appetite (which is the point), and sometimes mild fatigue. Rare but serious risks include pancreatitis, gallbladder problems, and severe dehydration if vomiting is significant. All three carry the same contraindications around medullary thyroid carcinoma and MEN2.

Practical comparison:

• Liraglutide has the highest reported rate of GI side effects per unit of weight loss — partly because the daily dosing keeps GLP-1 activity constant, partly because the dose-titration is faster than the weekly options.
• Semaglutide has a more tolerable per-unit GI profile than liraglutide, but still meaningful nausea during dose escalations.
• Tirzepatide appears to have less GI side effect intensity per unit of weight loss than semaglutide — possibly because the dual GIP/GLP-1 activity offsets some of the GLP-1-driven GI effects. This isn't universal; some patients tolerate semaglutide better.

For the month-by-month side effect pattern, see our side effects guide — the principles apply broadly across the three.

Cost and programme considerations

Pen prices vary by dose, supply, and provider. We don't list prices here because they change. The principles:

• Saxenda daily dosing means higher per-month pen cost than weekly options when measured per-month, despite individual vials being smaller.
• Wegovy weekly dosing is meaningfully cheaper per month than Saxenda at maintenance dose.
• Mounjaro weekly pen cost is similar to or slightly above Wegovy at equivalent maintenance positions, with larger average effect.

The bigger principle: compare programmes, not pens. A pen-only price doesn't include consultation, monitoring, dietary support, or clinician access for side effects. A responsible private programme bundles these. Cheap pen-only services are not the same product clinically — they're a sales channel without the safety scaffolding.

NHS access

All three have NICE technology appraisals supporting NHS use in specific contexts:

• Liraglutide (NICE TA664): through specialist weight management services for BMI ≥35 with non-diabetic hyperglycaemia and high risk of cardiovascular disease.
• Semaglutide (NICE TA875): through specialist weight management services for BMI ≥35 (≥32.5 in some ethnic groups) with at least one weight-related comorbidity. Two-year treatment cap.
• Tirzepatide (NICE TA1026): through specialist weight management services for similar BMI/comorbidity criteria.

NHS access in practice is limited by specialist service capacity. See NHS Tier 3 vs private weight loss for the comparison.

Who each medication suits

Saxenda might suit:

• Adolescents aged 12–17 with obesity (where weekly options aren't licensed).
• Adults who've tried weekly options and not tolerated them.
• Patients who prefer daily routine to weekly.
• Modest weight loss goals (5–10%) where the lower-efficacy profile is sufficient.
• Specific scenarios where supply or cost favours it.

Wegovy might suit:

• Patients who want the modern weekly schedule and an established 5+ year real-world track record.
• Patients with established cardiovascular disease (SELECT trial outcome data is the strongest of the three).
• Patients with prior tolerability issues with tirzepatide.
• Where supply or cost favours it at the time.
• Moderate weight loss goals (10–18%).

Mounjaro might suit:

• Patients with larger weight loss goals (≥15%).
• Patients who haven't responded sufficiently to Wegovy or Saxenda.
• Patients particularly sensitive to GI side effects (where the dual-agonist mechanism may help).
• Patients with type 2 diabetes alongside weight management (dual indication is convenient).
• Most first-time treatment-naïve adults seeking effective weight loss as of 2026.

For the dedicated Mounjaro vs Wegovy comparison, see our two-way comparison.

The structured programme requirement applies to all three

Following MHRA action on prescribing standards, every UK prescription of these medications must sit within a structured weight management programme. This isn't a sales pitch — it's a regulatory requirement, and it's there because the medication is one component of effective care, not the whole intervention.

A responsible programme includes:

• Clinical consultation before initiation, including BMI assessment, comorbidity check, and contraindication review.
• Dietary and behavioural support.
• Monitoring during dose escalation.
• Side effect management and clinical access.
• For women of reproductive age, contraception planning (see contraception guide).
• A clear plan for maintenance and discontinuation.

Compounded or non-regulated alternatives don't sit inside this structure. See our warning on compounded semaglutide for the safety case.

Decision framework

Useful sequence of questions:

1. What's the weight loss goal? Larger goals tilt toward tirzepatide; modest goals are well-served by semaglutide or even liraglutide.
2. Have you tried any GLP-1 before? Past tolerability is the best predictor of future tolerability.
3. What's your cardiovascular risk profile? Established CVD favours semaglutide for outcome-data reasons.
4. How sensitive are you to GI side effects? Tirzepatide may have a small edge; daily liraglutide tends to be the hardest of the three.
5. Daily vs weekly preference? If daily injection is a deal-breaker, that's two options ruled out.
6. What's the broader life context? Adolescent, pregnancy planning, type 2 diabetes, complex medication regimen — all influence the right choice.
7. What's available, where, at what cost, with what wraparound? The 'best' molecule is the one you can start, stay on, and be supported on.

The bigger picture

The three medications represent a real progression — not just marketing iteration. Saxenda established the GLP-1 weight management paradigm; Wegovy made it weekly and substantially more effective; Mounjaro added the dual-agonist mechanism for the largest effect to date. All three remain available, and all three have a place.

The decision between them isn't a product choice in isolation — it's a clinical decision based on you, made within a structured programme, by a prescriber who's not selling you a pen.

The next step

If you're trying to decide between Saxenda, Wegovy, and Mounjaro, the most useful single step is a 30-minute consultation. Bring your weight loss goal, any previous GLP-1 experience, your medical history, and any concerns about tolerability or cost. We'll work through the comparison in your specific context and — if appropriate — start the right one.