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
Mounjaro Dose vs Wegovy: How They Compare
If you're exploring weight loss injections in the UK, you've likely heard of both Mounjaro and Wegovy. Both are prescription-only medicines, but they work differently and use different dosing schedules. This guide compares Mounjaro dosing, Wegovy doses, and the clinical evidence behind each so you can understand the key differences. Your GP or a licensed prescriber will assess which is most suitable for you based on your individual health.
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.
Dosing Schedules and Trial Data
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — a key difference that affects how it works. It starts at 2.5 mg once weekly, escalating in 4-week intervals up to a maximum of 15 mg weekly. The SURMOUNT-1 clinical trial showed average weight loss of approximately 15% at 5 mg, 19.5% at 10 mg, and 20.9% at 15 mg over 72 weeks, alongside diet and exercise.
Wegovy (semaglutide) is a GLP-1 agonist only — it activates one hormone pathway rather than two. It starts lower at 0.25 mg weekly, titrating to 2.4 mg over 17 weeks. The STEP-1 trial showed average weight loss of approximately 14.9% at the maximum 2.4 mg dose over 68 weeks with lifestyle changes.
Both injections are once-weekly and available as pre-filled pens. The choice between them depends on prescriber assessment, your health profile, and individual response — no single option suits everyone. Our GLP-1 weight loss calculator can help you explore potential outcomes at different doses.
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 Is Right for You?
Neither Mounjaro nor Wegovy is universally "better" — individual results vary significantly. Some patients respond better to the dual GIP+GLP-1 mechanism of Mounjaro; others achieve good results on Wegovy's single GLP-1 pathway. Both require a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure.
Both are available through NHS specialist weight management services (tier 3) with potentially long waiting lists, or through private online prescribing with a UK-licensed prescriber. Your prescriber will consider your medical history, current medications, and any previous weight loss treatment experience. If you're uncertain about your eligibility, use our free BMI calculator to check your starting point, then discuss prescription options with your GP or a licensed healthcare professional.
- 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+GLP-1 receptor agonist (activates two hormone pathways), while Wegovy is a GLP-1 agonist only (one pathway). This dual mechanism is why Mounjaro uses higher doses — 2.5–15 mg weekly vs Wegovy's 0.25–2.4 mg. Both are once-weekly injections with similar weight loss outcomes on average, but individual responses vary.
Which injection caused more weight loss in clinical trials?
Mounjaro showed average weight loss of 20.9% at maximum dose in SURMOUNT-1, while Wegovy showed 14.9% in STEP-1. However, these trials used different populations and durations, so direct comparison isn't straightforward. Both are effective; individual results depend on dose, adherence, diet, and exercise.
Can I switch from Wegovy to Mounjaro on the NHS?
Switching between medications is a prescriber decision. If you're on NHS specialist weight management services, discuss switching options with your tier 3 service. Private prescribers can also manage switches. There's no official conversion chart — any change requires assessment by your prescriber.
How long does Mounjaro dose titration take?
Mounjaro titration takes a minimum of 20 weeks to reach maximum dose. You start at 2.5 mg for 4 weeks, then increase by 2.5 mg every 4 weeks: 5 mg (weeks 5–8), 7.5 mg (weeks 9–12), 10 mg (weeks 13–16), 12.5 mg (weeks 17–20), then 15 mg (week 21 onwards). Your prescriber may pause escalation if side effects occur.
Are Mounjaro and Wegovy available on the NHS in the UK?
Yes, both are UK-licensed and available on the NHS through specialist tier 3 weight management services, though availability and waiting times vary significantly by region. Both are also available privately through GPhC-registered online pharmacies following a clinical assessment by a UK-licensed prescriber.
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.