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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How to Buy Mounjaro Online in the UK — Wegovy Comparison
If you're looking to buy Mounjaro online in the UK, you need to understand how it compares to Wegovy and what the access process actually involves. Both are prescription-only weight loss injections available through UK-licensed prescribers following a clinical assessment. This guide explains the key differences between these two GLP-1 and dual-mechanism medications, how they work, what clinical trial data shows, and how to access them legally and safely in the UK. Neither medication is available over the counter — both require a prescription from a registered healthcare professional.
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Calculate Your BMI Instantly
Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
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.
Clinical Evidence: SURMOUNT vs STEP Trials
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — it works on two hormone pathways, not just one. In the SURMOUNT-1 clinical trial over 72 weeks, participants taking the maximum 15 mg dose lost an average of 20.9% of their body weight when combined with diet and exercise. The 10 mg dose achieved approximately clinically studied weight loss.
Wegovy (semaglutide) is a single GLP-1 receptor agonist. In the STEP-1 trial over 68 weeks, the maximum 2.4 mg dose resulted in an average weight loss of approximately 14.9% of body weight alongside lifestyle changes. Both sets of results are from randomised controlled trials — the gold standard of evidence. However, individual results vary considerably. Use our free GLP-1 weight loss calculator to estimate potential outcomes based on your starting weight and the dose your prescriber recommends.
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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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Mechanism, Doses & Access in the UK
The key mechanistic difference: Mounjaro activates both GIP and GLP-1 pathways, while Wegovy activates GLP-1 only. Mounjaro starts at 2.5 mg weekly and escalates to a maximum of 15 mg. Wegovy starts at 0.25 mg and reaches 2.4 mg maximum — both are once-weekly KwikPen injections. In the UK, both are accessed through NHS specialist weight management services (tier 3) with significant waiting lists, or through private online prescribing following a clinical consultation. A UK-licensed prescriber must assess whether either medication suits your individual health profile, BMI, and weight-related conditions. Neither is suitable for pregnant women, those under 18, or people with certain medical histories. Your prescriber will discuss eligibility during your 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.
Can I buy Mounjaro online without a prescription in the UK?
No. Mounjaro is prescription-only and requires a clinical assessment from a UK-licensed prescriber. You cannot legally purchase it without a valid prescription. Private online pharmacies require you to complete a health questionnaire, which is reviewed by a registered prescriber who then issues a prescription if appropriate. This is the legal and safe way to access Mounjaro online in the UK.
Is Mounjaro better than Wegovy for weight loss?
Clinical trials show Mounjaro achieved slightly higher average weight loss (20.9% at maximum dose) compared to Wegovy (14.9% at maximum dose). However, individual results vary significantly. Both medications work well for different people. Your prescriber will assess which is more suitable based on your medical history, other medications, and personal factors — not on trial averages alone.
How much does Mounjaro cost to buy online in the UK?
Private online Mounjaro costs vary by dose and provider, typically ranging from £129–£320 per month depending on which dose you're prescribed. NHS access is free but involves referral to specialist services with potential waiting lists. Private prescribers can provide cost information during consultation. Always check the total cost including the prescription fee.
Do I need NHS approval to buy Mounjaro online privately?
No. Private online prescribing is independent of the NHS. You do not need an NHS referral or GP approval to access Mounjaro privately online. However, you should inform your GP that you're taking it so they can monitor your health and adjust any other medications if needed. Your GP remains your primary healthcare contact.
What's the difference between tirzepatide and semaglutide?
Tirzepatide (Mounjaro) is a dual GIP+GLP-1 agonist. Semaglutide is a single GLP-1 agonist (Wegovy for weight loss, Ozempic for diabetes). The dual mechanism may explain why Mounjaro showed higher average weight loss in trials. Both are prescription-only in the UK and require clinical assessment. Your prescriber will help decide which suits you better.
Ready to take control of your weight loss journey?
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