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 Wegovy Dose Equals 5mg Mounjaro?
There is no official established conversion between Mounjaro and Wegovy doses, but clinical practice suggests that 5mg Mounjaro may be approximately equivalent to 0.5mg Wegovy in terms of intensity. However, both medications work differently and individual responses vary significantly. The choice between them depends on your personal health profile, not just dose equivalence. Your prescriber will assess which is more suitable for you based on clinical assessment, not simple dose conversion.
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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, meaning it activates two separate hormone pathways in your body. Wegovy (semaglutide) is a GLP-1-only receptor agonist, activating just one pathway. This fundamental difference in mechanism makes direct dose comparison misleading — a lower Mounjaro dose may produce effects similar to a higher Wegovy dose because Mounjaro works through two pathways simultaneously.
- Mounjaro: Dual action on GIP and GLP-1 receptors; maximum dose 15mg once weekly; SURMOUNT-1 trial showed ~20.9% average weight loss at 15mg
- Wegovy: Single GLP-1 pathway; maximum dose 2.4mg once weekly; STEP-1 trial showed ~14.9% average weight loss at 2.4mg
- Both are prescription-only and require clinical assessment before prescribing
- Both use the same injection frequency (once weekly) but have different KwikPen devices
The approximate 5mg Mounjaro to 0.5mg Wegovy equivalence is based on clinical practice observation, not official guidance — any switch between medications must be managed by your prescriber.
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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.
Why Your Prescriber Won't Simply Convert Doses
If you've been prescribed one medication and are considering the other, your prescriber will not simply "convert" your dose using an equivalence chart. Instead, they assess your individual suitability based on several factors: which mechanism (dual vs single pathway) suits your health profile, your tolerance of side effects so far, your medical history, and any other medications you take.
Both Mounjaro and Wegovy require a full clinical assessment before prescribing. You can use our free GLP-1 weight loss calculator to estimate potential outcomes at different doses, but this is educational only — your prescriber's decision is based on your complete health picture. If you're currently stable on one medication, switching is rarely recommended unless there's a specific clinical reason.
- 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 stronger than 0.5mg Wegovy?
They are not directly comparable due to different mechanisms. Mounjaro's dual GIP+GLP-1 action means 5mg may produce similar appetite-suppressing effects to a higher Wegovy dose. However, "stronger" depends on individual response — some people respond better to one medication than the other. Clinical trials showed different average weight loss percentages, but individual variation is significant.
Can I switch from Mounjaro to Wegovy without a new assessment?
No. Switching between prescription medications requires a new clinical assessment from your prescriber. They will evaluate whether the switch is appropriate for your health, assess your current dose, and potentially restart at a lower Wegovy dose with gradual titration. Never switch medications without prescriber guidance.
Which has fewer side effects — Mounjaro or Wegovy?
Both have similar common side effects (nausea, diarrhoea, constipation, stomach pain). Individual tolerance varies considerably. Some people experience fewer side effects on one medication than the other, but this cannot be predicted in advance. Your prescriber will help manage side effects if they occur.
Why aren't there official Mounjaro to Wegovy conversion guidelines in the UK?
Because the medications have different mechanisms of action and are approved as separate treatments, not interchangeable alternatives. The NHS and MHRA do not provide official conversion charts. Any prescriber switching you between medications bases this on individual clinical judgment, not a standard formula.
Can I use the GLP-1 weight loss calculator to compare Mounjaro and Wegovy results?
Our free GLP-1 weight loss calculator provides educational projections based on clinical trial averages, but individual results vary significantly. The calculator helps you understand potential outcomes at different doses — use it alongside your prescriber's advice, not instead of it. Your actual results depend on your specific health, adherence, diet, and activity level.
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.