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 and Mounjaro Equivalent Doses in the UK
Wegovy (semaglutide) and Mounjaro (tirzepatide) are both prescription-only weight management injections available in the UK, but they work differently and use different dose ranges. Understanding how their doses compare can help you discuss treatment options with your GP or prescriber. This guide explains the approximate equivalence between these medications and their NHS and UK prescribing context. Use our free BMI calculator to check your starting point, and our GLP-1 weight loss calculator to see potential outcomes at different doses.
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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.
Approximate Dose Equivalence and How They Compare
Wegovy (semaglutide) and Mounjaro (tirzepatide) are not directly interchangeable, but approximate dose equivalence can be estimated based on clinical trial data and prescribing practice. Mounjaro is a dual GIP and GLP-1 receptor agonist, whilst Wegovy is a GLP-1 agonist only — this difference affects potency and outcomes.
- Mounjaro 5 mg ≈ Wegovy 0.5 mg
- Mounjaro 10 mg ≈ Wegovy 1.7 mg
- Mounjaro 15 mg ≈ Wegovy 2.4 mg
These are approximate clinical equivalences only — not official NHS conversions. Individual response varies significantly. In UK clinical practice, switching between medications requires your prescriber's assessment and guidance. Neither medication assures specific weight loss outcomes. Average weight loss from Mounjaro in trials was approximately 15–21% body weight, whilst Wegovy showed approximately 14.9% at maximum dose, but results depend on dose, adherence, diet, and physical activity.
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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 Eligibility and UK Prescribing Routes for Both Medications
Both Wegovy and Mounjaro are available in the UK through two routes: NHS specialist weight management services (tier 3) and private online prescribing. NHS access is limited and varies significantly by region — many ICBs have long waiting lists or restricted criteria. NICE has approved both medications for use within NHS specialist services, but prescribing is not routine in primary care.
To be eligible for either medication, you typically need a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with a weight-related health condition such as type 2 diabetes, hypertension, or cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply. A prescriber must assess you individually before prescription. Your GP can refer you to tier 3 services, or you can access private prescribing after an online clinical consultation. Track your progress with our free progress tracker.
- 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?
Mounjaro and Wegovy work differently — Mounjaro is a dual GIP and GLP-1 agonist, whilst Wegovy is GLP-1 only. In clinical trials, Mounjaro showed slightly higher average weight loss (15–21%) than Wegovy (14.9%), but individual responses vary widely. Neither is universally "stronger" — suitability depends on individual health, tolerance, and prescriber assessment.
Can I switch from Wegovy to Mounjaro on the NHS?
Switching between medications on the NHS requires assessment by your specialist weight management service. There is no standard NHS switching protocol. Your prescriber will evaluate whether a switch is appropriate based on your response, side effects, and clinical need. Discuss any concerns with your tier 3 service or GP.
How long does it take to reach maximum dose with each medication?
Wegovy takes approximately 16 weeks to reach maximum dose (2.4 mg), with weekly dose increases. Mounjaro takes approximately 20 weeks to reach 15 mg, also with weekly increases. Both medications require a minimum of 4 weeks at each dose before escalation. This gradual titration helps your body adjust and minimises side effects.
Are Wegovy and Mounjaro available on the NHS in my area?
Availability varies significantly across UK regions and integrated care boards (ICBs). Some areas have established tier 3 weight management services offering GLP-1 medications; others have limited or no access. Contact your GP to ask about referral to local specialist services, or check your local ICB website for weight management commissioning details.
What are the main side effects of Wegovy and Mounjaro?
Both medications commonly cause nausea, diarrhoea, constipation, and stomach discomfort — usually mild and temporary. Mounjaro may also cause injection site reactions and fatigue. Serious side effects are rare but include severe stomach pain (possible pancreatitis) and gallbladder problems. Always report new or worsening symptoms to your prescriber immediately. ```
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