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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Cheaper Alternative to Mounjaro in the UK
If you're considering weight loss medication in the UK, Wegovy (semaglutide) is often the most affordable prescription alternative to Mounjaro (tirzepatide). Both are GLP-1 receptor agonist injections licensed for weight management, but they differ in mechanism, dosing schedules, and cost. This guide explains how to access Wegovy on the NHS, what private prescription costs typically are, and how the two medications compare in terms of price and availability across the UK.
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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.
Wegovy vs Mounjaro: Cost Comparison and Access in the UK
Wegovy (semaglutide) is typically the most affordable alternative to Mounjaro in the UK private market. At private prescription clinics, Wegovy costs generally range from £129 to £200 per month depending on the dose and provider. Mounjaro, by contrast, usually costs between £150 and £250 per month privately.
Key differences:
- Mechanism: Mounjaro is a dual GIP and GLP-1 agonist; Wegovy is GLP-1 only
- Dosing: Both are once-weekly injections, but tirzepatide starts at 2.5 mg and reaches 15 mg maximum; semaglutide starts at 0.25 mg and reaches 2.4 mg
- Average weight loss: Clinical trials showed Mounjaro ~15–21% body weight; Wegovy ~15% body weight at maximum dose
- Availability: Both available through NHS specialist services (waiting lists vary) and private online prescribing
Neither medication is inexpensive, but Wegovy often represents a lower entry-point cost for private users. Your GP or a licensed prescriber can assess which is more suitable for your individual circumstances.
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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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How to Access Wegovy: NHS vs Private Routes in the UK
NHS access: Both Mounjaro and Wegovy are available through NHS tier 3 specialist weight management services. However, access is regional, and waiting lists can be substantial—sometimes 12 months or longer depending on your ICB area. You'll need a GP referral and an assessment at a specialist clinic.
Private access: If NHS waiting times are prohibitive, Wegovy is available privately through UK-licensed online prescribers. The process is straightforward: complete an online health questionnaire, have a consultation with a registered prescriber (usually via phone or video), receive a prescription if approved, and collect from a GPhC-registered pharmacy. Costs are typically £129–£200 per month. Use our free GLP-1 weight loss calculator to estimate potential outcomes before committing to any medication.
- 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 Wegovy definitely cheaper than Mounjaro in the UK?
Often yes, but prices vary by clinic and dose. Wegovy typically ranges £129–£200/month privately, while Mounjaro is usually £150–£250/month. Lower starting doses are cheaper than maximum doses. Compare quotes from different UK prescribers before deciding.
Can I get Wegovy free on the NHS?
Yes, through NHS tier 3 specialist weight management services following a GP referral. However, regional waiting lists are often very long—sometimes 6–18 months. Eligibility requires a BMI of 30+ or 27+ with weight-related health conditions. Availability depends on your local ICB.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist with higher maximum doses (15 mg). Wegovy (semaglutide) is GLP-1 only with a lower maximum dose (2.4 mg). Clinical trials showed Mounjaro slightly higher average weight loss, but individual results vary. Both are once-weekly injections.
How long does a Wegovy pen last?
Each Wegovy pen contains 4 weekly doses (one month's supply). At the standard maintenance dose of 2.4 mg once weekly, one pen lasts 4 weeks. Cost per month depends on your provider and dose level.
Do I need a prescription for Wegovy or Mounjaro in the UK?
Yes, both are prescription-only medicines in the UK. You cannot buy them over the counter or online without a valid UK prescription from a licensed prescriber. Access is via NHS referral or private online consultation with a registered GP or nurse prescriber.
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