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 vs Mounjaro: Dose Comparison for NHS Patients
Both Wegovy (semaglutide) and Mounjaro (tirzepatide) are prescription-only weight management injections available in the UK, but they differ significantly in how they work and how they're dosed. This guide explains the dose differences, UK eligibility criteria, and how to access each medication through NHS specialist services or private prescribing. Our free GLP-1 weight loss calculator can help you understand potential outcomes at different doses.
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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.
NHS Eligibility and Dose Ranges Explained
In the UK, both medications are licensed for adults with a BMI of 30 kg/m² or above, or 25–29.9 kg/m² with weight-related health conditions like type 2 diabetes, hypertension, or cardiovascular disease. Wegovy uses a single mechanism (GLP-1 receptor agonist), while Mounjaro is a dual GIP and GLP-1 receptor agonist — this difference affects dosing schedules.
Wegovy doses: Start at 0.25 mg weekly, escalating in steps through 0.5 mg, 1 mg, 1.7 mg, and reaching a maximum of 2.4 mg per week at week 17 onwards. Most patients reach maintenance at 1.7 mg or 2.4 mg.
Mounjaro doses: Start at 2.5 mg weekly, escalating through 5 mg, 7.5 mg, 10 mg, 12.5 mg, and reaching 15 mg as maximum. Each dose is held for a minimum of 4 weeks before escalation. NICE has approved tirzepatide (Mounjaro) for use within NHS specialist weight management services, though access varies significantly by region.
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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.
NHS vs Private Access Routes in the UK
NHS access to both Wegovy and Mounjaro requires referral to a tier 3 specialist weight management service from your GP. These services assess eligibility, prescribe medication, and provide ongoing support. However, waiting times for NHS specialist services can be several months to years in many areas due to high demand.
Private access is available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber. This route is faster but involves costs (typically £129–£320+ monthly depending on dose and provider). Whichever route you choose, use our free BMI calculator to understand your current classification and discuss options with your GP or prescriber.
- 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 key difference between Wegovy and Mounjaro dosing?
Wegovy uses a single GLP-1 mechanism with a smaller maximum dose (2.4 mg per week), while Mounjaro is a dual GIP/GLP-1 agonist with a higher maximum dose (15 mg per week). Mounjaro also has larger dose increments. Both require minimum 4-week intervals between dose increases on the NHS.
Which medication is easier to access through the NHS?
Both require NHS specialist tier 3 referral, but NICE has approved Mounjaro specifically for NHS weight management services. Availability depends on your regional Integrated Care Board (ICB). Private access bypasses NHS waiting lists but involves upfront costs. Check with your local NHS weight management service first.
Can I switch from Wegovy to Mounjaro on the NHS?
Potentially, but any switch must be managed by your NHS prescriber or specialist service. There's no official established conversion chart between the two — approximate equivalences exist (e.g., Wegovy 2.4 mg ≈ Mounjaro 10–15 mg) but individual suitability varies. Discuss with your specialist if you're considering a change.
What does MHRA "Black Triangle" status mean for Mounjaro in the UK?
Mounjaro holds additional MHRA monitoring (Black Triangle ▼ status), meaning it's under enhanced surveillance for safety. This is routine for newer medicines and doesn't mean it's unsafe — it simply reflects that post-market monitoring is ongoing. Always report side effects to your GP or pharmacist.
How long does it take to reach the maximum dose on each medication?
Wegovy reaches maximum (2.4 mg) by week 17 with 4-week intervals between doses. Mounjaro reaches maximum (15 mg) by week 21, also with 4-week intervals. Most patients benefit at intermediate doses without reaching maximum — your prescriber will titrate based on tolerance and effectiveness.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.