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 10 mg vs Wegovy — What's the Difference?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight loss injections licensed in the UK, but they work differently and have different dosing schedules. Mounjaro's 10 mg dose sits mid-range in its escalation pathway, whilst Wegovy reaches its maximum at 2.4 mg — a much lower absolute dose. This guide compares the two directly so you understand the key differences. Both require clinical assessment and are prescribed alongside diet and lifestyle changes. Our GLP-1 weight loss calculator can help you explore potential outcomes with either medication.
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.
How Mounjaro 10 mg and Wegovy Compare — Clinical Trial Data
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — it activates two natural hormone pathways simultaneously. The SURMOUNT-1 clinical trial showed that at 10 mg weekly, tirzepatide helped participants lose an average of 19.5% of their body weight over 72 weeks, alongside a reduced-calorie diet and increased physical activity.
Wegovy (semaglutide) is a GLP-1 receptor agonist only — it activates one pathway. The STEP-1 trial showed that at its maximum dose of 2.4 mg weekly, semaglutide helped participants lose approximately 14.9% of body weight over 68 weeks under similar lifestyle conditions.
The key difference: Mounjaro's dual mechanism may offer greater average weight loss in clinical settings, but individual results vary significantly. Both are given as once-weekly injections via a pre-filled pen (Mounjaro uses a KwikPen). Neither medication assures specific weight loss for any individual.
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.
Eligibility, Prescription Access, and Individual Suitability
Both Mounjaro and Wegovy are prescribed to UK adults with a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions such as type 2 diabetes, hypertension, or sleep apnoea. Lower BMI thresholds may apply if you are of South Asian, Chinese, Black African, or Black Caribbean heritage. Access is via NHS specialist weight management services (with significant regional variation and waiting lists) or through private prescription following an online clinical assessment. Your prescriber will assess your individual medical history, current medications, and suitability — neither medication is right for everyone. Use our BMI calculator to check your personal BMI and understand where you sit on NHS guidance thresholds.
- 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 Mounjaro 10 mg stronger than Wegovy 2.4 mg?
Mounjaro's 10 mg dose resulted in approximately 19.5% average weight loss in clinical trials, whilst Wegovy 2.4 mg achieved approximately 14.9%. However, these are trial averages — individual results vary widely. Mounjaro's dual GIP+GLP-1 mechanism differs from Wegovy's GLP-1-only mechanism, but strength cannot be directly compared. Only a prescriber can assess which suits your individual health profile.
Can you switch from Mounjaro to Wegovy or vice versa?
Any switch between medications must be managed by your prescriber. Approximate dose equivalences exist (e.g. Mounjaro 10 mg is roughly equivalent to Wegovy 1.7 mg), but there is no official conversion chart. Switching requires stopping one medication and careful initiation of the other with proper timing — never switch without medical supervision.
How much does Mounjaro 10 mg cost in the UK?
Mounjaro costs approximately £145–£175 per KwikPen (4 weeks supply) through private prescribing services, depending on the provider. A single KwikPen contains four 10 mg doses. NHS access is free but only through specialist tier 3 weight management services, with regional waiting lists that can be months long.
What are the main side effects of Mounjaro at 10 mg?
Common side effects include nausea, diarrhoea, constipation, vomiting, and stomach pain — typically most pronounced when dosing up and often improve with time. Injection site reactions are also common. Both Mounjaro and Wegovy carry similar gastrointestinal side effect profiles. Always seek urgent medical attention for severe stomach pain, as this may indicate pancreatitis.
How long does Mounjaro 10 mg stay in your system?
Mounjaro has a half-life of approximately 4–5 days, meaning the medication gradually leaves your body after each injection. Because you inject once weekly, a steady state builds up. If you stop treatment, it typically takes about 2–3 weeks for the medication to clear your system completely, though appetite changes may persist longer.
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.