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
Free tracker included with every download this week
How Much Mounjaro vs Wegovy — What's the Difference?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight management injections available in the UK, but they work differently and come in different doses. This guide explains the key differences between them, how they compare in clinical trials, and how a prescriber decides which might suit you. Both require a clinical assessment before prescription.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
Mounjaro vs Wegovy — Doses and Mechanisms
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways to regulate appetite and support feeling fuller after meals. It starts at 2.5 mg and escalates weekly to a maximum of 15 mg.
Wegovy (semaglutide) is a GLP-1 receptor agonist only, activating a single hormone pathway. It begins at 0.25 mg and escalates over 16 weeks to a maximum of 2.4 mg.
- Mounjaro: once-weekly injection, maximum dose 15 mg
- Wegovy: once-weekly injection, maximum dose 2.4 mg
- Different mechanisms mean different body responses — individual suitability varies
In clinical trials, Mounjaro showed average weight loss of approximately 15–21% of body weight, whilst Wegovy showed approximately 15% at maximum dose. However, individual results vary significantly, and both are used alongside reduced-calorie diet and increased physical activity.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Which Medication Is Right for You?
Neither Mounjaro nor Wegovy is "better" overall — suitability depends on your individual health circumstances, medical history, and how your body responds. A UK-licensed prescriber will assess eligibility based on your BMI, weight-related health conditions, and any contraindications.
Both medications require a clinical assessment before prescription. If you have a BMI of 30 or above, or 27–29.9 with weight-related conditions like type 2 diabetes or hypertension, you may be eligible for either medication through NHS specialist services or private online prescribing.
Calculate your personal BMI using our free BMI calculator above, then discuss options with your GP or a prescriber. Your individual health profile, not the medication name, determines the right choice for you.
- 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 main difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP and GLP-1 receptor agonist (two hormone pathways), whilst Wegovy is a GLP-1 agonist only (one pathway). This dual mechanism is why Mounjaro doses are measured in milligrams up to 15 mg, whilst Wegovy goes up to 2.4 mg. Different mechanisms can produce different individual responses.
How much weight loss can I expect with Mounjaro or Wegovy?
Clinical trials showed Mounjaro users lost approximately 15–21% of body weight on average, and Wegovy users approximately 15% on average. However, individual results vary significantly. Weight loss depends on dose, adherence, diet, activity level, and individual metabolism. A prescriber can discuss realistic expectations based on your circumstances.
Are Mounjaro and Wegovy available on the NHS in the UK?
Yes, both are NHS-approved. Access is through specialist tier 3 weight management services, typically following a GP referral. Waiting times and availability vary significantly by region. Private prescribing is also available through GPhC-registered online services following an online clinical assessment.
How often do I inject Mounjaro or Wegovy?
Both are once-weekly injections. Mounjaro comes as a pre-filled KwikPen with 4 doses (4 weeks supply). Wegovy also comes as a pre-filled pen. Injection sites can be rotated between stomach, thigh, or upper arm.
Can I switch from Mounjaro to Wegovy or vice versa?
Switching between medications must be managed by a prescriber. Approximate equivalence exists (5 mg Mounjaro ≈ 0.5 mg Wegovy, 15 mg Mounjaro ≈ 2.4 mg Wegovy), but any switch requires clinical oversight. Your prescriber will assess whether a switch is appropriate and manage the transition safely.
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.