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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Mounjaro and Wegovy Dose Equivalents in the UK
Mounjaro (tirzepatide) and Wegovy (semaglutide) are both prescription-only weight management injections available in the UK, but their doses are not directly interchangeable. While approximate dose equivalences exist based on clinical practice, any switch between these medications must be managed by your prescriber. Understanding how dosing differs helps clarify why these two GLP-1 and GIP/GLP-1 medications work differently in your body. Use our free BMI calculator to check your current health status and eligibility for weight management treatment.
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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 and NHS Context
While Mounjaro and Wegovy both support weight management through different mechanisms, there is no official NHS-approved conversion between them. However, clinical practice suggests approximate equivalence:
- Mounjaro 5 mg ≈ Wegovy 0.5 mg (both initiation/early escalation)
- Mounjaro 10 mg ≈ Wegovy 1.7 mg (mid-range maintenance)
- Mounjaro 15 mg ≈ Wegovy 2.4 mg (maximum doses)
Key difference: Mounjaro is a dual GIP and GLP-1 agonist, while Wegovy is a GLP-1 agonist only. This means Mounjaro activates two hormone pathways, potentially explaining why it showed ~20.9% average weight loss in clinical trials compared to Wegovy's ~14.9% in STEP trials. Both require a prescription following clinical assessment by a UK prescriber, and NICE has approved tirzepatide (Mounjaro) for use within NHS specialist services.
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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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NHS Access, Eligibility, and Private Routes in the UK
NHS access: Both medications may be prescribed through tier 3 specialist weight management services following GP referral, though regional availability and waiting times vary significantly. Eligibility requires a BMI of 30 kg/m² or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, hypertension, or cardiovascular disease. For South Asian, Chinese, Black African, or Black Caribbean adults, lower thresholds may apply.
Private access: Both Mounjaro and Wegovy are available through private online prescribing following a consultation with a UK-licensed prescriber. Individual results vary, and either medication is used alongside a reduced-calorie diet and increased physical activity. Try our GLP-1 weight loss calculator to project potential outcomes at different doses.
- 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 switch from Mounjaro to Wegovy at an equivalent dose?
No direct official conversion exists. Any switch must be managed by your prescriber, who may adjust your starting dose. Because Mounjaro is a dual agonist and Wegovy is a single agonist, they work differently. Never self-switch between prescription medications — always consult your prescriber first.
Which is more effective, Mounjaro or Wegovy?
Clinical trials showed Mounjaro achieved approximately 20.9% average weight loss versus Wegovy's 14.9%. However, individual results vary significantly. Effectiveness depends on your personal metabolism, adherence, diet, and activity level. Your prescriber can help determine which is most suitable for you.
Are both Mounjaro and Wegovy available on the NHS in the UK?
Yes, both are available through NHS tier 3 specialist weight management services following GP referral, though availability and waiting times vary by region. NICE has approved tirzepatide (Mounjaro) for NHS use. Access depends on local ICB provision and your eligibility.
What's the difference between Mounjaro's mechanism and Wegovy's?
Mounjaro activates both GIP and GLP-1 receptor pathways, while Wegovy activates GLP-1 only. This dual action may explain Mounjaro's higher average weight loss in trials. Both slow gastric emptying and support appetite regulation, but through slightly different biological mechanisms.
How do I know which weight loss injection is right for me?
Your GP or a UK prescriber will assess your medical history, BMI, comorbidities, and any contraindications. Both require a prescription. Use our BMI calculator to understand your current status, then discuss prescription weight management options with your healthcare provider. ```
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