Mounjaro vs Ozempic

If you're being prescribed either Mounjaro or Ozempic, the conversation has shifted in 2024-2025. Tirzepatide has matured into a real first-line contender. Here's how to think about the choice.

The SURPASS-2 trial randomised 1,879 adults with type 2 diabetes inadequately controlled on metformin to either tirzepatide (5, 10, or 15 mg weekly) or semaglutide 1 mg weekly. After 40 weeks: HbA1c reduction of 2.0-2.3% on tirzepatide vs 1.9% on semaglutide. Weight loss: 7.6-11.2 kg on tirzepatide vs 5.7 kg on semaglutide. Tirzepatide won on both outcomes, with the largest gaps at the 10 mg and 15 mg doses.

• Schedule: both weekly injections.
• Pen design: very similar.
• Storage: refrigerated, then room temperature in use.
• Side effect categories: nausea, constipation, reflux, fatigue.
• Rare serious risks: pancreatitis, gallstones, severe gastroparesis on both.
• Mechanism overlap: GLP-1 receptor activation in both. Tirzepatide adds GIP.

• Need maximum HbA1c reduction: lean Mounjaro on the SURPASS-2 evidence.
• Have established cardiovascular disease: Ozempic still has the strongest CV outcomes data (SUSTAIN-6). Tirzepatide CV trials are maturing.
• Already responding well to Ozempic: probably no reason to switch.
• Insufficient response on Ozempic 1 mg: ask about escalating to 2 mg first; consider Mounjaro if 2 mg also insufficient.
• Newly diagnosed: both reach therapeutic effect over a similar timescale, and the local pathway, supply and cost usually decide.

• In the UK, the licensed weight-loss versions are Mounjaro (under that brand for both diabetes and weight) or Wegovy (semaglutide branded for weight loss).
• Ozempic is NOT licensed for weight loss in the UK. If your reason is weight only, you'd be looking at Mounjaro vs Wegovy, not vs Ozempic.
• Mounjaro for weight loss on the NHS: recommended by NICE (TA1026) for adults with BMI ≥35 plus at least one weight-related condition, with lower thresholds (usually reduced by 2.5) for people from South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family backgrounds.
• On weight loss specifically: Mounjaro 15 mg → ~21% loss at 72 weeks (SURMOUNT-1); Wegovy 2.4 mg → ~15% at 68 weeks (STEP 1).

• Nausea: similar on both at equivalent therapeutic doses (in the SURPASS-2 head-to-head, ~17-22% on tirzepatide vs ~18% on semaglutide; higher in obesity trials, peaking around 30% at dose escalations).
• Constipation: Ozempic 1 mg ~6% (SUSTAIN/PIONEER); Mounjaro 5-15 mg ~6-9% (pooled SURPASS 1-5).
• Diarrhoea: Mounjaro slightly higher across all doses.
• Reflux: similar incidence on both.
• Hypoglycaemia: low risk on either as monotherapy. Higher when combined with sulfonylureas or insulin.
• Hair shedding: reported on both. It is thought to track rapid weight loss itself rather than the drug, and usually settles as weight stabilises.

This article is about comfort and everyday patterns, not medical guidance. Your doctor and pharmacist know you and your medicine; if anything about how you feel worries you, speak to them promptly, and if you ever feel seriously unwell, treat it as an emergency. The medicine's own patient information leaflet carries the important safety information and is worth reading in full.

• NHS for diabetes: both are routinely available; specific local pathways depend on the diabetes service.
• NHS for weight loss: Mounjaro can be initiated in primary care or specialist weight management services under NICE TA1026, with phased rollout. Capacity is limited.
• Private prescription: both £150-300/month depending on dose. Mounjaro often slightly cheaper at lower-equivalent doses.
• Supply: intermittent for both since 2023; Mounjaro has been more stable in late 2025.