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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Wegovy Equivalent to Mounjaro — Dosing Comparison
While Mounjaro (tirzepatide) and Wegovy (semaglutide) are both prescription weight management injections available in the UK, they work through different mechanisms and have different dose ranges. There is no direct 1:1 dose equivalence between them, though approximate comparisons exist based on clinical trial data and prescribing practice. This guide explains how the doses compare, how they differ, and what this means for your treatment options. Both are prescription-only medicines requiring a clinical assessment before dispensing.
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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
Clinically, approximate dose equivalences based on SURMOUNT and STEP trial data suggest:
- Mounjaro 5 mg ≈ Wegovy 0.5 mg — early escalation phase, modest appetite reduction
- Mounjaro 10 mg ≈ Wegovy 1.7 mg — mid-range maintenance, effective appetite suppression
- Mounjaro 15 mg (maximum) ≈ Wegovy 2.4 mg (maximum) — highest available doses
Important: These are clinical approximations only, not official conversion guidelines. Individual response varies significantly. Average weight loss with Mounjaro is slightly higher (15–21% body weight) than Wegovy (approximately 15% body weight), though both are used alongside reduced-calorie diet and increased physical activity. Any switch between medications must be managed by your prescriber.
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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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Key Differences Between Mounjaro and Wegovy
Mechanism: Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways. Wegovy is a GLP-1 receptor agonist only, activating a single pathway. This dual action in Mounjaro may explain slightly higher average weight loss in clinical trials.
Manufacturer: Mounjaro is made by Eli Lilly; Wegovy by Novo Nordisk. Both are available through NHS specialist weight management services and private online prescribing in the UK.
Injection schedule: Both are once-weekly. Mounjaro uses a KwikPen device; Wegovy uses an auto-injection pen. Both require a prescription and clinical assessment of your individual eligibility and health needs.
- 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 stronger than Wegovy?
Not necessarily "stronger" — they work differently. Mounjaro's dual mechanism (GIP + GLP-1) produces slightly higher average weight loss in trials (~21% vs ~15%), but individual results vary. Choice between them depends on your health profile, response, and prescriber assessment, not dose strength alone.
Can you switch from Wegovy to Mounjaro?
Yes, some people do switch if their prescriber judges it appropriate. However, there's no standard conversion protocol. Your prescriber would typically start Mounjaro at 2.5 mg and titrate upward, rather than calculating an exact equivalent dose. Any switch must be medically supervised.
Which has fewer side effects — Mounjaro or Wegovy?
Both cause similar side effects: nausea, diarrhoea, vomiting, constipation, and stomach pain are common early on. Side effect profiles are comparable. Individual tolerance varies. Your GP or prescriber can discuss which might suit your health situation better.
Why is there no official dose conversion between Mounjaro and Wegovy?
They're different medications with different mechanisms and dose ranges. There's no regulatory guidance establishing a formal conversion. Prescribers base switches on clinical experience and individual patient response, not a fixed formula.
How do I know which one I'm eligible for?
Eligibility is assessed by your prescriber based on BMI, health conditions, medications, and medical history — not on the dose or drug name. Both require a clinical assessment. Use our GLP-1 weight loss calculator to estimate potential outcomes, then discuss options with your GP or a licensed prescriber.
Ready to take control of your weight loss journey?
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