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: Dosage, Cost, and UK Access
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight management injections available in the UK, but they differ significantly in dosage schedules, maximum doses, and how you can access them. This guide compares both medications across dosing, cost, and whether you can get them through the NHS or private prescription. Understanding these differences helps you make an informed discussion with your GP or 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.
Dosage Comparison: Mounjaro vs Wegovy
Mounjaro (tirzepatide) starts at 2.5 mg once weekly, escalating by 2.5 mg every 4 weeks up to a maximum of 15 mg per week. Wegovy (semaglutide) begins at 0.25 mg, titrating through 0.5 mg, 1 mg, and 1.7 mg doses, with a maximum of 2.4 mg once weekly. In clinical trials, Mounjaro's dual GIP and GLP-1 mechanism produced average weight loss of around 15–21% body weight, whilst Wegovy demonstrated approximately 14.9% average loss at the maximum dose. Both require a minimum of 4 weeks at each dose before escalation. The kwikpen device for Mounjaro delivers 4 weekly doses per pen, whilst Wegovy uses an auto-injection pen system. Individual results vary significantly based on lifestyle changes, diet adherence, and personal metabolism.
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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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UK Cost and Private Access Routes
Private Mounjaro and Wegovy are available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber. Costs typically range from £129–£320 per month depending on the dose—higher doses cost more. A single Mounjaro kwikpen (4 weeks supply) at lower doses costs around £150–£200, whilst 15 mg pens may exceed £300. Wegovy pricing follows a similar scale. These prices exclude the prescriber consultation fee, which varies from £20–£50 depending on the provider. The NHS route is free at point of use but access is limited to specialist tier 3/4 weight management services, usually requiring a GP referral and involves potential waiting lists of several months in many areas. Private prescription is faster but involves upfront cost.
- 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.
What's the maximum dose of Mounjaro vs Wegovy?
Mounjaro reaches a maximum of 15 mg once weekly, whilst Wegovy's maximum is 2.4 mg once weekly. Mounjaro typically requires 20 weeks to reach the top dose, escalating in 2.5 mg increments. Wegovy reaches maximum after about 16–17 weeks. Both allow minimum 4-week intervals between increases.
Can I get Mounjaro or Wegovy on the NHS in the UK?
Yes, both are available through NHS specialist weight management services (tier 3/4), but access requires GP referral and eligibility assessment. Availability varies by region and NHS waiting lists can be lengthy. Private prescription routes are faster but cost approximately £150–£300 monthly depending on dose.
Is Mounjaro more expensive than Wegovy in the UK?
Pricing is similar—both range from around £129–£320 per month. Final cost depends on the dose you're prescribed. Lower starting doses cost less; maximum doses cost more. Private providers vary slightly, so it's worth comparing. NHS access is free but involves waiting times.
How long does each Mounjaro and Wegovy pen last?
A Mounjaro kwikpen contains 4 doses, lasting 4 weeks. Wegovy pens also contain 4 weeks' worth of doses at your current strength. You'll need to order a new pen or refill monthly during your escalation phase, then monthly once you reach your maintenance dose.
Which medication causes more weight loss—Mounjaro or Wegovy?
Clinical trials showed Mounjaro produced slightly higher average weight loss (15–21% body weight) compared to Wegovy (14.9%). However, individual results vary considerably based on adherence, diet, exercise, and metabolism. Your prescriber can discuss which might suit you better during a clinical assessment.
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