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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What Is 1 mg Wegovy Equivalent to Mounjaro?
There is no exact dose-for-dose equivalent between Wegovy (semaglutide) and Mounjaro (tirzepatide) because they work differently in your body. Whilst both are once-weekly weight loss injections licensed in the UK, Wegovy is a single GLP-1 receptor agonist, whereas Mounjaro is a dual GIP and GLP-1 agonist. Approximately 1 mg Wegovy may be comparable to around 5–7.5 mg Mounjaro in terms of clinical effect, but this varies significantly between individuals. Any switch between medications must be managed by your prescriber following a clinical assessment.
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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.
Wegovy vs Mounjaro: Dose Comparison and Mechanism Differences
Approximate dose equivalence: 1 mg Wegovy is sometimes considered roughly equivalent to 5–7.5 mg Mounjaro, though this is not an official conversion and is based on clinical practice experience rather than head-to-head trials.
Why the difference matters: Mounjaro's dual GIP and GLP-1 mechanism means it may have a stronger effect at lower doses compared to Wegovy's single GLP-1 pathway. In the STEP clinical trial, 1 mg Wegovy produced average weight loss of approximately 6–7% of body weight over 68 weeks. In contrast, the SURMOUNT trial showed Mounjaro's 5 mg dose achieved approximately clinically studied weight loss on average.
Individual variation: Weight loss outcomes depend on many factors including your starting weight, metabolism, diet, activity level, and how your body responds to the medication. Your GLP-1 weight loss calculator can help estimate potential outcomes at different doses.
- Wegovy doses: 0.25 mg → 0.5 mg → 1 mg → 1.7 mg → 2.4 mg (maximum)
- Mounjaro doses: 2.5 mg → 5 mg → 7.5 mg → 10 mg → 12.5 mg → 15 mg (maximum)
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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
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Switching Between Medications: When and How
If you are currently taking Wegovy and your prescriber suggests switching to Mounjaro (or vice versa), never switch doses based on mathematical equivalence alone. Your prescriber will assess your individual response and may restart you on a lower dose of the new medication to monitor tolerance and safety.
In the UK, switching between weight loss injections typically involves a clinical consultation with your prescriber or GP. They will review your weight loss progress, any side effects experienced, your current health conditions, and your weight loss goals. You may need to pause medication between switching, or your prescriber may overlap doses depending on circumstances. Always inform your prescriber of any other medications you take, as absorption interactions can occur with GLP-1 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.
Is 1 mg Wegovy the same strength as 5 mg Mounjaro?
Not exactly. Whilst 1 mg Wegovy and 5 mg Mounjaro may produce similar weight loss effects on average, they are not pharmacologically equivalent. Mounjaro's dual GIP and GLP-1 action means lower doses may achieve comparable results to Wegovy. Any dose comparison must be made by your prescriber based on your individual response and health status.
Can I switch from 1 mg Wegovy to Mounjaro myself?
No. Switching between GLP-1 medications requires a clinical assessment from your prescriber or GP. Never change doses or switch medications without medical guidance. Your prescriber will decide the appropriate Mounjaro starting dose for you, which is typically lower than your Wegovy dose, and monitor your response carefully.
Which medication causes more weight loss — Wegovy or Mounjaro?
Clinical trial data suggests Mounjaro may produce slightly greater average weight loss (approximately 15–21% body weight) compared to Wegovy (approximately 14.9% body weight). However, individual results vary significantly, and the "best" medication depends on your personal response, side effect tolerance, and health conditions. Your prescriber will recommend the most suitable option for you.
Why don't Wegovy and Mounjaro have standard dose equivalents?
Because they use different mechanisms. Mounjaro's dual GIP and GLP-1 action is more potent than Wegovy's single GLP-1 pathway, meaning lower Mounjaro doses may match higher Wegovy doses. Additionally, weight loss depends on individual factors beyond just the medication dose, making universal equivalence impossible.
Is Mounjaro available on the NHS in the UK?
Mounjaro (tirzepatide) has been approved by NICE for NHS use within specialist weight management services for eligible adults. Access varies by region and ICB (Integrated Care Board). Your GP can refer you to your local tier 3 specialist weight management service. Private prescribing is also available through UK-licensed online providers following a clinical assessment.
Ready to take control of your weight loss journey?
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