Ozempic vs Wegovy vs Mounjaro — UK Comparison 2026

The plain-English verdict: Mounjaro produces the most weight loss, Wegovy has more approvals, and Ozempic isn’t for weight loss at all in the UK. All three are GLP-1 receptor agonist injections — but they are not the same drug, they are not approved for the same conditions, and their prices, eligibility rules, and effectiveness differ significantly. This guide cuts through the confusion with real current data.

⚠️ Medical disclaimer: This article is for informational purposes only. Always consult a registered UK healthcare professional before starting or switching any weight-loss medication. These are prescription-only medicines.

The Key Difference — In One Sentence

Ozempic (semaglutide) is a diabetes drug used off-label for weight loss. Wegovy (semaglutide) is the same drug at a higher dose, licensed specifically for weight loss. Mounjaro (tirzepatide) is a different drug entirely — it targets two appetite hormones rather than one, and produces significantly more weight loss than either.

Head-to-Head Comparison

What Are These Drugs and How Do They Work?

All three drugs belong to a class called GLP-1 receptor agonists. They work by mimicking a hormone naturally released after eating — GLP-1 (glucagon-like peptide-1) — which signals to the brain that you are full, slows digestion, and reduces appetite. The result is that you eat less, crave less, and your body burns stored fat.

Mounjaro goes a step further. In addition to GLP-1, tirzepatide also mimics a second appetite-regulating hormone called GIP (glucose-dependent insulinotropic polypeptide) — making it a dual-action drug. This two-hormone mechanism is why Mounjaro consistently produces greater weight loss than semaglutide-based drugs in clinical trials.

Effectiveness — What the Research Shows

The most significant head-to-head trial comparing Mounjaro and Wegovy was published in the New England Journal of Medicine in May 2025, following presentation at the European Congress on Obesity.

The results were decisive:

• Mounjaro: 20.2% average body weight reduction after 72 weeks
• Wegovy: 13.7% average body weight reduction after 72 weeks
• 32% of Mounjaro users lost more than a quarter of their body weight, vs 16% on Wegovy
• Average waist reduction: 18cm on Mounjaro vs 13cm on Wegovy
• Side effects were comparable — around 77–79% of users reported at least one (mostly digestive issues) — but slightly more Wegovy users (8%) stopped early due to side effects vs Mounjaro (6%)

Professor Naveed Sattar from the University of Glasgow told the BBC: “Private sales of tirzepatide have now surpassed those of semaglutide in the UK — and I expect this paper will further accelerate that trend.”

The important caveat: Wegovy is currently approved in the UK to reduce the risk of serious heart problems in people with obesity, including heart attack and stroke prevention. Equivalent heart protection trials for Mounjaro are still ongoing — meaning Wegovy has a broader clinical approval profile beyond just weight loss.

Ozempic vs Wegovy — What’s the Difference?

Many people are confused by Ozempic and Wegovy because they contain the exact same drug — semaglutide. The difference is in dose and approval.

Ozempic is approved in the UK only for type 2 diabetes — not weight loss. It comes in doses up to 1mg per week.

Wegovy is approved specifically for obesity/weight management, at a higher maximum dose of 2.4mg per week, and produces greater weight loss as a result.

Superdrug Online Doctor explains: “In the UK, Wegovy is licensed as a weight loss injection while Ozempic is approved for lowering blood sugar levels in type 2 diabetes.” While Ozempic is sometimes prescribed off-label for weight loss privately, this is a grey area. For weight loss purposes, Wegovy is the clinically appropriate and licensed choice.

Private Costs in the UK — Current Prices (May 2026)

Mounjaro (Tirzepatide) Private Prices

Source: WePrescribe price comparison, updated 12 May 2026.

💡 Note on Mounjaro pricing: Eli Lilly raised list prices by up to 170% in September 2025, with the highest dose originally set to hit £330/month. Following BBC reporting, Eli Lilly offered a discounted rate to suppliers of £247.50 for the max dose — limiting, but not eliminating, the consumer price increase. Always compare before purchasing.

Wegovy (Semaglutide) Private Prices

Source: Medino price comparison, updated March 2026.

NHS Access — Who Qualifies?

The NHS uses a phased rollout for both Wegovy and Mounjaro. Access is not available via a standard GP appointment — both must be prescribed through a specialist weight management service.

Wegovy (Semaglutide) — NHS Eligibility

NHS England stipulates:

• BMI of 35 or above (or 32.5+ for South Asian, Black African, Black Caribbean, Middle Eastern, or Chinese populations)
• Must have at least one weight-related health condition (e.g. hypertension, type 2 diabetes, sleep apnoea, dyslipidaemia, cardiovascular disease)
• Must be referred to and prescribed by a specialist weight management service — not directly by a GP

Mounjaro (Tirzepatide) — NHS Eligibility

Currently more restrictive — NHS England’s Phase 1 criteria require:

• BMI of 40 or above (adjusted for ethnicity)
• At least four of the following five conditions: high blood pressure, high cholesterol/blood fats, obstructive sleep apnoea, heart disease, type 2 diabetes
• Must be prescribed via a specialist weight management service
• Patient must also engage in diet, exercise, and behavioural support alongside medication

CutKilo confirms that Mounjaro was NICE-approved in 2025 for adults with BMI ≥ 35 with at least one weight-related condition, but the NHS rollout in primary care settings (GP practices) remains phased — with highest clinical need patients prioritised first.

Ozempic — NHS Weight Loss Access

Ozempic is not available on the NHS for weight loss. It is prescribed only for type 2 diabetes management. If you have type 2 diabetes and are seeking weight loss, your doctor may consider Ozempic for glycaemic control (with weight loss as a secondary benefit), but Wegovy would be the appropriate prescription for weight loss as a primary goal.

Side Effects — What to Expect

Side effects are broadly similar across all three drugs, as they work on the same hormonal pathways.

Most common (affecting 20–40% of users):

• Nausea — most common, especially at dose escalation; typically improves over time
• Vomiting
• Diarrhoea or constipation
• Stomach discomfort / bloating
• Reduced appetite (intentional effect — but can feel unpleasant initially)

Less common but important:

• Fatigue, especially in early weeks
• Headaches
• Injection site reactions (mild redness or swelling)
• Gallstones — risk increases with rapid weight loss on any GLP-1 drug
• Pancreatitis — rare but serious; seek immediate medical attention if you develop severe abdominal pain

Who should NOT take these drugs:

• Pregnant or breastfeeding women
• People with a personal or family history of thyroid cancer (specifically medullary thyroid carcinoma)
• People with MEN2 syndrome
• Those with a history of pancreatitis (discuss with your doctor)
• People with severe digestive conditions (gastroparesis)

Which Drug Is Right for You?

Frequently Asked Questions