Mounjaro vs Wegovy UK: Which Is Better for Weight Loss? (2026)

Mounjaro vs Wegovy — which weight loss injection is better? Both are once-weekly GLP-1 injections prescribed for weight loss in the UK, but clinical trials show Mounjaro (tirzepatide) produces significantly more weight loss than Wegovy (semaglutide). This guide compares them head-to-head on effectiveness, side effects, cost, and UK availability so you can decide which is right for you.

How they work

Wegovy (semaglutide 2.4mg) targets a single receptor — GLP-1. It slows gastric emptying, reduces appetite, and helps regulate blood sugar.

Mounjaro (tirzepatide) targets two receptors — GLP-1 and GIP. This dual mechanism is why clinical trials consistently show greater weight loss with Mounjaro compared to Wegovy.

Weight loss: what the trials show

| | Mounjaro (15mg) | Wegovy (2.4mg) | |---|---|---| | Average weight loss | 22.5% of body weight | 15% of body weight | | Trial | SURMOUNT-1 | STEP 1 | | Duration | 72 weeks | 68 weeks | | Participants losing >20% | 57% | 32% |

The SURMOUNT-1 trial showed that patients on the highest Mounjaro dose lost an average of 22.5% of their body weight — roughly 7 percentage points more than Wegovy.

In the head-to-head SURMOUNT-5 trial, Mounjaro demonstrated statistically superior weight loss compared to Wegovy at every dose level.

Dosing schedule

Both are once-weekly injections, but the dose escalation differs:

Mounjaro: Start at 2.5mg, escalate every 4 weeks through 5mg, 7.5mg, 10mg, 12.5mg, up to 15mg.

Wegovy: Start at 0.25mg, escalate monthly through 0.5mg, 1mg, 1.7mg, up to 2.4mg maintenance.

Both take approximately 4–5 months to reach the maintenance dose.

Side effects

Side effects are similar for both medications and are predominantly gastrointestinal:

• Nausea (most common, usually subsides after 4–6 weeks)
• Diarrhoea
• Constipation
• Vomiting
• Abdominal pain

Mounjaro tends to cause slightly more GI side effects during dose escalation, but this is generally proportional to its greater effectiveness.

Cost comparison

This is where the picture gets interesting. Despite being the more effective drug, Mounjaro is often cheaper than Wegovy from UK private providers.

| | Mounjaro (starter) | Wegovy (starter) | |---|---|---| | Typical price range | £35–55/week | £40–65/week | | Includes consultation? | Usually yes | Usually yes |

Prices vary significantly between providers. Some include ongoing monitoring, prescriber access, and dose adjustments in the price; others charge separately.

Who is eligible?

Both medications require a prescription and are indicated for adults with:

• BMI of 30 or above (obese), or
• BMI of 27 or above (overweight) with at least one weight-related condition (e.g., type 2 diabetes, high blood pressure, sleep apnoea)

A clinical consultation is required before prescribing. Most UK online providers include this in their price.

NHS availability

Wegovy is available on the NHS through specialist weight management services, but access is limited and waiting lists are long.

Mounjaro received NICE approval for weight management in late 2024 and is gradually being rolled out through NHS specialist services.

In practice, the vast majority of patients access both medications privately due to NHS waiting times.

Which should you choose?

Choose Mounjaro if:

• Maximum weight loss is your priority
• You want the most clinically effective option
• You prefer a potentially lower weekly cost

Choose Wegovy if:

• You have a longer track record preference (Wegovy was licensed first)
• Your provider only stocks Wegovy
• You had GI issues with tirzepatide previously

For most patients, Mounjaro offers better value: more weight loss at a similar or lower price point.

Compare prices now

The best way to find the right option is to compare current prices from verified UK providers. All providers listed on Treatcompare are GPhC-registered pharmacies or CQC-regulated healthcare services.

Related guides

• Mounjaro vs Wegovy Side Effects — detailed side effect comparison
• How Much Does Mounjaro Cost? — full pricing breakdown by dose
• How Much Does Wegovy Cost? — Wegovy pricing guide
• Ozempic vs Wegovy — same drug, different doses
• GLP-1 Weight Loss Injections: Complete Guide — all options explained