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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Is Wegovy 0.5mg Equivalent to Mounjaro?
Wegovy (semaglutide) 0.5mg and Mounjaro (tirzepatide) are not directly equivalent — they're different medications with different mechanisms. Wegovy is a GLP-1 receptor agonist, while Mounjaro is a dual GIP and GLP-1 agonist. In clinical terms, the closest Mounjaro equivalent to Wegovy 0.5mg would be around 2.5–5mg, but direct comparisons are challenging because the medications work differently. This guide explains the differences and what equivalent dosing means in UK weight management practice.
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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.
How Wegovy and Mounjaro Work Differently
Wegovy (semaglutide) activates only the GLP-1 hormone pathway — it signals fullness to the brain and slows stomach emptying. Mounjaro (tirzepatide) activates both GLP-1 and GIP pathways, providing dual hormone control. This difference means they don't have a simple one-to-one dose equivalent. Wegovy's 0.5mg is typically a dose adjustment week (taken between weeks 5–8 of the titration schedule), whereas Mounjaro's 2.5mg is a starting dose. In clinical trials, Mounjaro showed slightly higher average weight loss (~20.9% at maximum dose) compared to Wegovy (~14.9% at maximum dose), but individual results vary significantly. Both are prescription-only medicines requiring a clinical assessment from a licensed prescriber before being prescribed. A prescriber will assess your individual circumstances and determine which medication, if either, is appropriate for you.
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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
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Approximate Dose Comparisons (For Context Only)
If you're comparing doses, approximate clinical equivalence suggests: Wegovy 0.5mg ≈ Mounjaro 2.5–5mg, Wegovy 1mg ≈ Mounjaro 7.5mg, and Wegovy 2.4mg ≈ Mounjaro 10–15mg. However, these are rough approximations based on clinical practice — there is no official established conversion chart because the medicines work through different mechanisms. If you're currently taking Wegovy and considering switching to Mounjaro (or vice versa), this must be managed by your prescriber, not self-directed. Use our free GLP-1 weight loss calculator to estimate potential outcomes with either medication, and discuss with your GP or prescriber which option might suit your health needs best.
- 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 0.5mg the same strength as Mounjaro 0.5mg?
No. Wegovy 0.5mg and Mounjaro 0.5mg are not equivalent — they contain different active ingredients (semaglutide vs tirzepatide) and work through different pathways. Mounjaro 0.5mg is not a standard dose; Mounjaro starts at 2.5mg. Always compare medications through their clinical evidence and prescriber guidance, not just number values.
Can I switch from Wegovy 0.5mg to Mounjaro 0.5mg?
Any switch between medications must be managed by your prescriber. Do not change or switch medications on your own. Your GP or licensed prescriber will assess your individual health, review your current treatment, and determine if a switch is appropriate and at what dose. There may be a transition period required.
Which is more effective — Wegovy or Mounjaro?
Clinical trials show Mounjaro achieved slightly higher average weight loss (~20.9%) than Wegovy (~14.9%), but individual results vary significantly. Effectiveness depends on your personal response, adherence, lifestyle changes, and health factors. Your prescriber will recommend the most suitable option based on your circumstances, not on average trial data.
Why don't Wegovy and Mounjaro have exact dose equivalents?
Because they work through different hormone pathways. Wegovy uses GLP-1 only; Mounjaro uses both GLP-1 and GIP. This dual mechanism in Mounjaro means a lower mg dose can achieve similar effects to a higher Wegovy dose. Direct equivalence is not clinically straightforward.
Is Wegovy available on the NHS in the UK?
Wegovy (semaglutide) is licensed for weight management in the UK. NHS access is through specialist tier 3 weight management services via GP referral, though availability and waiting lists vary significantly by region. Private prescribing through online consultations is also available. Check your local NHS integrated care board for current availability.
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