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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Mounjaro 10ml vs Wegovy — What's the Difference?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight management injections licensed in the UK, but they work differently and come in different doses. Mounjaro's 10mg dose is an intermediate step in its titration schedule, whilst Wegovy reaches its maximum at 2.4mg. This guide compares the two medications side-by-side so you understand how they differ, what clinical trials showed, and how a prescriber will decide which might suit your situation.
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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.
How Mounjaro and Wegovy Work Differently
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — it activates two natural hormone pathways simultaneously. This dual mechanism may help regulate appetite, reduce food cravings, and support satiety more effectively than single-pathway medications.
Wegovy (semaglutide) is a GLP-1 receptor agonist only — it activates the GLP-1 pathway alone. This single mechanism is also effective but works through one hormonal route rather than two.
In the SURMOUNT-1 clinical trial, Mounjaro at 10mg showed average weight loss of approximately 19.5% of body weight over 72 weeks. In the STEP-1 trial, Wegovy at its maximum 2.4mg dose showed average weight loss of approximately 14.9% of body weight over 68 weeks. However, individual results vary significantly, and these are trial averages alongside reduced-calorie diet and increased physical activity.
Your prescriber will discuss which mechanism might work better for your individual health profile and weight loss goals.
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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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Doses and How They Compare
Mounjaro doses: Starting at 2.5mg, increasing weekly to 5mg, 7.5mg, 10mg, 12.5mg, and up to 15mg maximum. The 10mg dose is typically reached around week 13–16 of treatment. It's an intermediate step, not the maximum.
Wegovy doses: Starting at 0.25mg, increasing through 0.5mg, 1mg, 1.7mg, and reaching 2.4mg maximum around week 17+. Wegovy's maximum dose is lower in absolute terms than Mounjaro's, reflecting the different potency of the two medications.
Both are once-weekly injections. Your prescriber determines your starting dose and pace of increase based on how you tolerate the medication. Use our free GLP-1 weight loss calculator to explore potential outcomes at different doses.
Both medications are prescription-only in the UK and require a clinical assessment before being prescribed. Your GP or a UK-licensed prescriber will review your medical history, current medications, BMI, and weight-related health conditions to determine which is more appropriate for you. Access via the NHS involves referral to a specialist tier 3 weight management service; private prescribing is available through online assessment. Neither medication is assured to work, and individual suitability depends on your personal health profile, not just dose size.
Check your BMI using our free BMI calculator to understand your starting point, then discuss eligibility with your 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.
Which causes fewer side effects — Mounjaro or Wegovy?
Both cause similar common side effects (nausea, diarrhoea, constipation, abdominal pain). Clinical trials suggest nausea is very common with both. Individual tolerance varies widely. Your prescriber can discuss which may suit you better based on your medical history. Neither is universally "safer" — it's personal.
Is Mounjaro 10mg equivalent to Wegovy 2.4mg?
Not directly. Mounjaro 10mg and Wegovy 2.4mg are not pharmacologically equivalent — they're different medications with different potency. Approximate clinical equivalence suggests Mounjaro 10mg is roughly equivalent to Wegovy 1.7mg based on trial data, but this is not an official conversion. Your prescriber determines dosing individually.
Can you switch from Wegovy to Mounjaro at 10mg?
Switching between medications requires prescriber guidance. There is no official established conversion chart. A prescriber may step you up gradually onto Mounjaro starting at 2.5mg, not jump directly to 10mg. Any medication switch must be managed medically, not self-directed.
Are both available on the NHS in the UK?
Both Mounjaro and Wegovy are approved for use within NHS specialist weight management services (tier 3), but availability varies significantly by region and waiting lists can be very long. Private prescribing via online assessment is also available for both. Your GP can discuss NHS access in your area.
How do I know which one is right for me?
This is a decision for your prescriber after clinical assessment. Factors include your medical history, other medications, weight-related health conditions, tolerability of GLP-1 medications, and individual response. Neither is "better" universally — suitability is personal. Book a consultation to discuss your options.
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.