Mounjaro (tirzepatide) and Saxenda (liraglutide 3 mg) are both injectable weight-loss medications available in the UK, but they differ significantly in mechanism, efficacy and convenience. This comparison helps you understand which might suit you better.
How They Work
Saxenda is a GLP-1 receptor agonist. It mimics the GLP-1 hormone to reduce appetite and slow gastric emptying. Mounjaro is a dual GIP and GLP-1 receptor agonist, targeting two incretin pathways simultaneously. This dual action is believed to be the reason behind Mounjaro’s greater efficacy in clinical trials.
Efficacy
- Saxenda: Average weight loss of approximately 8% of body weight over 56 weeks in the SCALE trials.
- Mounjaro: Average weight loss of 15–22% of body weight over 72 weeks in the SURMOUNT trials, depending on dose.
Mounjaro consistently demonstrates roughly double the average weight loss compared to Saxenda.
Dosing and Convenience
| Feature | Mounjaro | Saxenda |
|---|---|---|
| Frequency | Once weekly | Once daily |
| Device | Pre-filled KwikPen | Pre-filled pen with dose dial |
| Titration | 2.5 mg → up to 15 mg over several months | 0.6 mg → 3 mg over 5 weeks |
| Injection sites | Abdomen, thigh, upper arm | Abdomen, thigh, upper arm |
Mounjaro’s once-weekly dosing is a major convenience advantage. Saxenda requires daily injections, which some patients find burdensome.
Side Effects
Both medications share common GI side effects: nausea, vomiting, diarrhoea and constipation. Saxenda’s daily dosing means side effects may be more constant, while Mounjaro’s side effects often peak in the one to two days following injection and then ease.
Cost in the UK
Saxenda is available on private prescription and typically costs £150–£250 per month. Mounjaro costs approximately £150–£300 per month depending on dose and pharmacy. Prices vary between online pharmacies, which is why using a comparison tool like MedsLens can save you significant money over the course of treatment.
NHS Availability
As of late 2025, Mounjaro has received NICE approval for weight management alongside diet and exercise in eligible adults. Saxenda has been available on the NHS for longer but is less commonly prescribed due to lower efficacy and daily dosing burden.
Which Should You Choose?
For most patients, Mounjaro offers superior weight loss with more convenient dosing. Saxenda may still suit those who prefer a medication with a longer track record or who cannot tolerate tirzepatide. Always discuss options with your prescriber to find the best fit for your individual circumstances.