The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
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Mounjaro vs Wegovy — Which Costs Less in the UK?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight loss injections available in the UK, but their costs differ significantly. The cost of either medication depends on which dose you're prescribed and whether you access them through the NHS or privately. This guide compares the pricing, eligibility criteria, and how each medication works so you can understand the full picture before speaking to your GP or a licensed prescriber.
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What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
How Mounjaro and Wegovy Pricing Differs
Mounjaro (tirzepatide) typically costs between £120–£320 per month depending on the dose prescribed and the provider. The Mounjaro KwikPen device contains four weekly injections, so monthly costs reflect the dose strength (2.5 mg, 5 mg, 10 mg, or higher up to the maximum 15 mg).
Wegovy (semaglutide) generally costs between £140–£310 per month at doses ranging from 0.5 mg to the maximum 2.4 mg weekly. Both medications require a subscription model through private prescribing services, as NHS access is extremely limited and involves long waiting lists.
- Mounjaro starting dose: 2.5 mg (lowest cost entry point)
- Wegovy starting dose: 0.25 mg (very gradual titration)
- Both increase by 0.5–1 mg increments over 16+ weeks
- Maximum maintenance dose determines long-term monthly cost
Neither medication has consistent NHS availability outside specialist tier 3 weight management services. Private prescribing via online consultation is the fastest and most reliable access route in the UK currently.
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
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Clinical Differences That Affect Suitability
Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways simultaneously. Wegovy is a GLP-1 receptor agonist only, activating one pathway. In clinical trials, Mounjaro showed slightly higher average weight loss (~15–21% body weight) compared to Wegovy (~15% body weight), though individual results vary significantly.
The choice between them isn't primarily about cost — it's about which your prescriber determines is appropriate for your individual health profile. Both require a clinical assessment, both have similar eligibility criteria (BMI ≥30, or ≥27 with weight-related health conditions), and both may cause similar side effects including nausea, diarrhoea, and constipation. Use our GLP-1 weight loss calculator to explore potential outcomes at different doses, and use the BMI calculator to check your current status before consultation.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
Is Mounjaro cheaper than Wegovy in the UK?
Pricing is similar overall (£120–£320/month for both), but varies by dose and private provider. Mounjaro's lowest starting dose (2.5 mg) may cost slightly less initially than Wegovy, but both reach similar maximum monthly costs. Price alone shouldn't determine choice — your prescriber will recommend based on clinical suitability.
Can I get Mounjaro or Wegovy free on the NHS?
NHS access is extremely limited and only through specialist tier 3 weight management services following GP referral. Waiting lists are often 6–12+ months in many regions. Private prescribing via online consultation is currently the fastest UK access route, requiring a clinical assessment from a UK-licensed prescriber.
What's the difference between Mounjaro and Wegovy mechanisms?
Mounjaro (tirzepatide) activates both GIP and GLP-1 receptors (dual action), whilst Wegovy (semaglutide) activates GLP-1 only. The dual action in Mounjaro may contribute to slightly greater average weight loss in clinical trials, but individual responses vary. Both work by reducing appetite and promoting satiety.
How long does a Mounjaro KwikPen last?
One Mounjaro KwikPen contains four weekly injections, so it lasts exactly one month. You'll need a new pen each month. Costs are usually quoted per month or per pen. Unopened pens must be refrigerated; once in use, they can be kept at room temperature (below 30°C) for up to 30 days.
Which medication will my GP prescribe — Mounjaro or Wegovy?
Your GP or prescriber will recommend based on your individual health history, current medications, and clinical assessment. Neither is inherently "better" — suitability varies per person. Both require a prescription and clinical assessment. If you have specific health conditions or concerns, discuss these with your prescriber before starting either medication.
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