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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What Dose of Mounjaro vs Wegovy? UK Comparison
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight loss injections available in the UK, but they work on different mechanisms and use different dose schedules. Mounjaro is a dual GIP and GLP-1 receptor agonist starting at 2.5 mg weekly, while Wegovy is a GLP-1 agonist only, starting at 0.25 mg weekly. Understanding the dose ranges and how they compare can help you discuss which option might suit your individual health needs with your GP or prescriber.
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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.
Mounjaro vs Wegovy Dose Ranges and Titration
Mounjaro (tirzepatide) comes in a dose range from 2.5 mg to 15 mg, administered once weekly via pre-filled KwikPen. Starting at 2.5 mg, the dose escalates every 4 weeks: 5 mg, 7.5 mg, 10 mg, 12.5 mg, and finally 15 mg as the maximum maintenance dose.
Wegovy (semaglutide) has a lower starting dose of 0.25 mg weekly, escalating to 0.5 mg, 1 mg, 1.7 mg, and 2.4 mg as the maximum dose. This gentler titration schedule may reduce early side effects for some people.
- Mounjaro: steeper starting dose, fewer escalation steps, reaches higher absolute dose
- Wegovy: lower starting dose, five escalation steps, takes longer to reach maintenance
- Both require minimum 4 weeks at each dose before increasing
- Both administered as once-weekly injections
Clinical trial data from SURMOUNT-1 (Mounjaro) showed average weight loss of 20.9% at the 15 mg dose, whilst STEP-1 (Wegovy) showed approximately 14.9% average weight loss at 2.4 mg, though individual results vary significantly.
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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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Choosing Between the Doses: Prescriber Assessment
Neither medication is "stronger" or "better" — they use different mechanisms, and suitability depends on your individual health profile, medical history, and how your body responds during titration. Some people tolerate Mounjaro's dual GIP+GLP-1 mechanism better; others find Wegovy's single GLP-1 pathway more suitable.
Your prescriber will assess eligibility based on BMI (30 kg/m² or above, or 27+ with weight-related health conditions), current medications, kidney function, and any history of pancreatitis or thyroid problems. They will also discuss side effects — both medications can cause nausea, diarrhoea, and constipation during the titration phase — and help you decide which medication and starting dose aligns with your health goals and tolerability.
Use our free GLP-1 weight loss calculator above to explore projected outcomes at different doses, and our BMI calculator to check where you stand currently against NHS 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.
What's the difference between Mounjaro and Wegovy doses?
Mounjaro starts at 2.5 mg and goes up to 15 mg once weekly; Wegovy starts at 0.25 mg and reaches 2.4 mg once weekly. Mounjaro escalates faster but has higher absolute doses. Both require 4 weeks minimum at each dose before increasing. The dose you need depends on individual factors your prescriber will assess.
Which medication reaches its highest dose faster?
Mounjaro reaches its maximum dose (15 mg) faster due to larger dose increments and fewer escalation steps. Wegovy has a gentler escalation with five smaller steps before reaching 2.4 mg, which may suit people sensitive to side effects during titration.
Does higher dose mean more weight loss?
Clinical trials showed greater average weight loss at higher doses for both medications. However, individual results vary significantly. Some people see meaningful weight loss at lower maintenance doses, whilst others benefit from reaching maximum dose. Your prescriber will recommend the appropriate dose for your situation.
Can I start on a higher Mounjaro dose?
No. UK prescribing guidelines require starting at 2.5 mg and titrating upwards every 4 weeks. Starting higher increases side effect risk and is not recommended. Your prescriber must follow this escalation protocol for safety.
Is Mounjaro available on the NHS as Mounjaro KwikPen?
Mounjaro (tirzepatide) is NICE-approved and available through NHS specialist tier 3 weight management services, though regional availability varies significantly. Private prescriptions are also available through UK-licensed online prescribers. Access routes and waiting times differ by area.
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.