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 1 Mg vs Mounjaro — Understanding Dose Equivalence in the UK
Wegovy 1 mg and Mounjaro contain different active ingredients and are not directly equivalent on a milligram-for-milligram basis. Wegovy contains semaglutide (a GLP-1 receptor agonist), whilst Mounjaro contains tirzepatide (a dual GIP and GLP-1 agonist). In UK clinical practice, approximate dose equivalence suggests that Wegovy 1 mg is roughly comparable to Mounjaro 5 mg in terms of weight loss effect, though individual responses vary significantly. This guide explains how these medications compare under NHS and UK private prescribing, and what dose equivalence means for your health.
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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.
NHS Prescribing, Eligibility, and Dose Comparison
Both Wegovy and Mounjaro are prescription-only medicines licensed in the UK for weight management in adults with a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes or cardiovascular disease. The MHRA has approved both medications, and both are available through NHS specialist tier 3 weight management services where capacity exists, though access varies significantly by region. Dose equivalence is approximate: clinical practice suggests Wegovy 1 mg is roughly comparable to Mounjaro 5 mg, Wegovy 1.7 mg to Mounjaro 10 mg, and Wegovy 2.4 mg (maximum) to Mounjaro 15 mg (maximum). However, these are clinical estimates only—no formal NHS conversion chart exists. The STEP trial (Wegovy) and SURMOUNT-1 trial (Mounjaro) showed similar average weight loss outcomes at maximum doses (approximately 15% body weight for Wegovy 2.4 mg, and 20.9% for Mounjaro 15 mg), though individual results vary. Always consult your GP or prescriber about which medication is most suitable for your specific health situation.
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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.
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NHS vs Private Access for Wegovy in the UK
NHS access to Wegovy is through specialist weight management services (tier 3), requiring a referral from your GP. Waiting lists in many areas are lengthy—months to years in some regions—and availability depends on your local Integrated Care Board (ICB). Private prescribing via UK-licensed online services is faster; a clinical assessment typically takes days, and the medication can be dispensed by a GPhC-registered pharmacy. Private costs range from approximately £129–£200 per month depending on dose and provider. Regardless of route, Wegovy requires a prescription following clinical assessment. A licensed prescriber will evaluate your BMI, weight-related health conditions, medication interactions, and suitability before issuing a prescription. Use our free GLP-1 weight loss calculator to explore 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.
What's the difference between Wegovy 1 mg and Mounjaro 5 mg?
Wegovy contains semaglutide (GLP-1 only); Mounjaro contains tirzepatide (dual GIP+GLP-1). Wegovy 1 mg and Mounjaro 5 mg are approximate clinical equivalents for weight loss effect, but they work differently. Individual responses vary. A prescriber will recommend the most suitable option for you.
Can I switch from Wegovy to Mounjaro on the NHS?
Switching between medications requires prescriber guidance. NHS specialist services may consider a switch if one medication is ineffective or poorly tolerated. Any change must be managed by your specialist team—do not stop one medication and start another without medical supervision.
Is Mounjaro better than Wegovy for weight loss?
Clinical trials suggest Mounjaro may produce slightly greater average weight loss at maximum dose (20.9% vs 14.9%), but individual outcomes vary considerably. "Better" depends on your personal health, tolerability, and response. Your GP or specialist will assess which is more appropriate for you.
How long does it take to reach Wegovy 1 mg on NHS?
Wegovy titration takes approximately 5–8 weeks to reach 1 mg: starting at 0.25 mg (weeks 1–4), then escalating to 0.5 mg (weeks 5–8), then 1 mg (week 9+). Titration may be slower if side effects occur. Your prescriber adjusts the schedule based on your response.
What does "dose equivalence" really mean in practice?
Approximate dose equivalence refers to similar weight loss outcomes observed in clinical trials at comparable doses. It does not mean the medications are identical—they work via different mechanisms. Your individual response depends on genetics, lifestyle, and overall health, not just the dose number.
Ready to take control of your weight loss journey?
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