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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Going Up to 5mg Mounjaro — Comparison With Wegovy
Moving from the starting dose to 5mg Mounjaro marks your first maintenance dose in the tirzepatide titration schedule. At this stage, many people compare Mounjaro directly with Wegovy to understand which medication might suit them better. Both are prescription-only weight management injections licensed in the UK, but they work differently and have different dosing schedules. This guide explains the clinical trial evidence, mechanism differences, and eligibility criteria to help you understand what your prescriber considers when choosing between them.
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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 5mg Mounjaro Compares to Wegovy
Mounjaro (tirzepatide) at 5mg is a dual GIP and GLP-1 receptor agonist — it activates two separate hormone pathways, whereas Wegovy (semaglutide) activates only the GLP-1 pathway. In the SURMOUNT-1 clinical trial, participants on 5mg Mounjaro lost approximately 15% of their body weight on average over 72 weeks, alongside a reduced-calorie diet and increased physical activity. STEP-1 trial data for Wegovy at 2.4mg showed approximately 14.9% average weight loss, though Wegovy's maintenance dose (2.4mg) is higher than Mounjaro's 5mg. Both injections are once-weekly, but Mounjaro requires fewer dose steps to reach maintenance. Individual results vary significantly, and both medications cause similar side effects — primarily nausea, diarrhoea, and constipation in the early weeks. Neither medication is a standalone solution; both require lifestyle changes including reduced-calorie eating and increased activity.
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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.
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 — Individual Assessment
Your prescriber will assess your suitability based on your individual health, medical history, and preferences — not just comparative trial data. Both Mounjaro and Wegovy require a UK prescription and clinical assessment before dispensing. Eligibility is the same for both: BMI 30 or above, or BMI 27–29.9 with at least one weight-related health condition (type 2 diabetes, hypertension, dyslipidaemia, sleep apnoea, or cardiovascular disease). Lower BMI thresholds apply for South Asian, Chinese, Black African, and Black Caribbean adults. Try our GLP-1 weight loss calculator to explore projected weight loss at different doses, and use our BMI calculator to check your current category — both tools help frame the conversation 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.
Is 5mg Mounjaro equivalent to Wegovy 2.4mg?
No exact equivalence exists. 5mg Mounjaro and Wegovy 2.4mg are not directly comparable doses because Mounjaro is a dual GIP+GLP-1 agonist while Wegovy is GLP-1 only. Clinical trials show similar average weight loss (15–15% body weight), but mechanisms differ. Your prescriber chooses based on your individual health profile, not dose equivalence.
What side effects should I expect when increasing to 5mg Mounjaro?
The most common side effects at any Mounjaro dose include nausea, diarrhoea, vomiting, and stomach pain. Many people experience fewer nausea symptoms after the first few weeks as their body adjusts. Side effects typically decrease over time. Always report persistent or severe symptoms to your prescriber.
Can I switch from Wegovy to Mounjaro mid-treatment in the UK?
Yes, switching is possible but must be managed by your prescriber. There is no official NHS conversion chart between medications. Your prescriber will assess whether switching is appropriate for your health and will guide you through any transition period. Never switch without clinical guidance.
How long does it take to reach 5mg Mounjaro, and is that the maximum dose?
You reach 5mg Mounjaro by week 5 of treatment (2.5mg for weeks 1–4, then 5mg from week 5 onwards). The maximum dose is 15mg once weekly, typically reached by week 21. Your prescriber may adjust your dose based on how you respond and any side effects you experience.
Does the NHS prescribe Mounjaro or Wegovy for weight management?
Yes, both are now approved by NICE for NHS use within specialist tier 3 weight management services. However, NHS access varies significantly by region and availability. Waiting lists can be lengthy. Private online prescribing through GPhC-registered pharmacies offers faster access but involves a cost, typically £129–£320 monthly depending on dose.
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.