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
Free tracker included with every download this week
Mounjaro vs Wegovy: Dose Equivalent and UK Access Options
Mounjaro (tirzepatide) and Wegovy (semaglutide) are both prescription-only GLP-1 and GIP weight loss injections available in the UK, but they work differently and cost differently depending on how you access them. While they're not directly equivalent in dosing — Mounjaro operates on a dual GIP and GLP-1 receptor pathway whereas Wegovy uses GLP-1 only — clinical data suggests approximate potency comparisons. This guide explains dose relationships, UK costs, and how to access each medication through NHS or private routes.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
Approximate Dose Equivalence and Cost Context
There is no official established dose conversion between Mounjaro and Wegovy, but clinical practice and trial data suggest approximate equivalences:
- Mounjaro 5 mg ≈ Wegovy 0.5 mg (early escalation)
- Mounjaro 10 mg ≈ Wegovy 1.7 mg (mid-range maintenance)
- Mounjaro 15 mg ≈ Wegovy 2.4 mg (maximum doses)
These are approximate comparisons only — individual response varies significantly. Mounjaro's dual mechanism may produce stronger appetite suppression at lower absolute doses than Wegovy's single GLP-1 pathway. In the SURMOUNT-1 trial, Mounjaro 15 mg achieved approximately 20.9% average body weight loss, whilst Wegovy's STEP-1 trial showed approximately 14.9% at 2.4 mg. Private UK prescriptions for Mounjaro typically cost £150–£320 per month depending on dose; Wegovy typically costs £129–£299 per month. Exact costs vary between online pharmacy providers. Both require a clinical assessment before prescription.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
NHS Access vs Private Prescription Routes
NHS access: Both medications are available through NHS specialist tier 3/4 weight management services following GP referral, but availability and waiting times vary dramatically by region (integrated care board). Many areas have waiting lists of several months to years. NHS prescriptions are free once prescribed, but access is the limiting factor.
Private access: Available through UK-licensed prescribers via online consultation with GPhC-registered pharmacies. No NHS referral needed. Requires completion of a health questionnaire and clinical assessment by a UK doctor. Processing typically takes 2–7 working days. Use our GLP-1 weight loss calculator to compare projected outcomes at different doses — this can help inform your choice between the two medications.
- 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 main difference between Mounjaro and Wegovy in how they work?
Mounjaro is a dual GIP and GLP-1 receptor agonist — it activates two hormone pathways simultaneously. Wegovy is a GLP-1 receptor agonist only, activating a single pathway. This dual mechanism may explain why Mounjaro achieves slightly higher average weight loss in clinical trials, though individual results vary significantly.
Can I switch from Wegovy to Mounjaro on the NHS?
Potentially, but this depends on your local weight management service. Any switch between medications must be managed by your prescriber. There is no automatic switch pathway — discuss with your specialist if you're not seeing adequate results on Wegovy after adequate time at therapeutic dose.
How long does a private online prescription take for either medication?
After your online clinical assessment is approved, most GPhC-registered pharmacies dispense within 2–7 working days. You'll receive your injection by post. This is significantly faster than many NHS referral pathways, though private costs apply (typically £150–£320/month).
Are Mounjaro and Wegovy interchangeable if I can't tolerate one?
Not automatically. They have different side effect profiles and mechanisms. Some people tolerate one better than the other. Your prescriber can assess whether switching is appropriate based on your specific side effects and response. Any switch requires medical supervision.
Which is cheaper — Mounjaro or Wegovy on prescription in the UK?
On average, Wegovy tends to be slightly cheaper (from approximately £129/month at starter doses) compared to Mounjaro (from approximately £150/month). However, costs vary between private providers and depend on the specific dose you're prescribed. Always check current pricing with individual pharmacies before committing.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.