With injectable weight-loss and diabetes medications becoming more widely available in the UK, many patients are asking: should I choose Mounjaro or Ozempic? Both are effective, but they have important differences in how they work, their clinical results, and their cost.
The Key Difference: Mechanism of Action
The most significant distinction is the drug target:
- Ozempic (semaglutide) targets only the GLP-1 receptor
- Mounjaro (tirzepatide) targets both GLP-1 and GIP receptors
This dual action gives Mounjaro a broader hormonal effect on appetite, blood sugar, and metabolism.
Weight Loss Comparison
Head-to-head data from the SURPASS-2 trial showed that tirzepatide outperformed semaglutide for weight reduction. Across broader trials:
- Ozempic (STEP trials): average weight loss of around 12–15% of body weight
- Mounjaro (SURMOUNT trials): average weight loss of around 18–22.5% of body weight at the highest dose
While individual results vary, the data consistently favours tirzepatide for weight reduction.
Blood Sugar Control
Both medications effectively lower HbA1c in patients with type 2 diabetes. However, tirzepatide achieved greater HbA1c reductions in the SURPASS-2 trial compared to semaglutide 1 mg, with more patients reaching target levels below 7%.
Side Effects
The side-effect profiles are similar. Both medications commonly cause:
- Nausea (especially during dose escalation)
- Diarrhoea or constipation
- Reduced appetite
- Injection site reactions
Gastrointestinal side effects tend to be most pronounced in the first few weeks and typically settle as your body adjusts.
Dosing Schedule
Both Mounjaro and Ozempic are injected once weekly. Ozempic is available in 0.25 mg, 0.5 mg, 1 mg, and 2 mg doses. Mounjaro comes in a wider range: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg.
Cost in the UK
Pricing varies considerably depending on whether you access these medications via the NHS or a private prescription. At the time of writing, a month's supply of Mounjaro through a private pharmacy typically ranges from £150 to £250 depending on the dose, while Ozempic can range from £100 to £200. Comparing prices on MedsLens can help you find the most affordable option from a registered UK pharmacy.
Which Should You Choose?
The right choice depends on your individual health profile, treatment goals, and budget. Speak with your GP or prescriber about which medication is most appropriate. Both are clinically proven, safe, and effective treatments for the right patient.