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
Can Anyone Take Mounjaro?
No, not everyone can take Mounjaro. In the UK, tirzepatide (Mounjaro) is a prescription-only medicine with specific eligibility criteria based on BMI, health conditions, age, and medical history. A prescriber must assess whether it's suitable for you following a clinical evaluation. Understanding who can and cannot take Mounjaro — and how it compares to Wegovy — helps you make informed decisions about weight management options. Both medications work differently and suit different people.
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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: Mechanism and Trial Data
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, meaning it activates two hormone pathways. Clinical trials (SURMOUNT-1) showed average weight loss of approximately 15–21% of body weight at the maximum 15mg dose over 72 weeks, alongside a reduced-calorie diet and increased physical activity.
Wegovy (semaglutide) is a GLP-1 receptor agonist only — it activates a single hormone pathway. STEP-1 trial data showed average weight loss of approximately 14.9% of body weight at the maximum 2.4mg dose over 68 weeks, with similar lifestyle support.
The dual mechanism of Mounjaro may theoretically offer advantages, but individual results vary significantly. Clinical trial averages do not predict personal outcomes. Your suitability depends on your health profile, not just which medication causes greater average weight loss. A prescriber will assess which is more appropriate for your circumstances.
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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.
UK Eligibility: Who Can and Cannot Take Mounjaro
You may be eligible for Mounjaro if you:
- Are 18 or over
- Have a BMI of 30 kg/m² or above, OR BMI of 27–29.9 with a weight-related health condition (type 2 diabetes, prediabetes, high blood pressure, abnormal blood fats, sleep apnoea, or cardiovascular disease)
- Have lower BMI eligibility if you are of South Asian, Chinese, Black African, or Black Caribbean heritage (from approximately BMI 27.5)
You cannot take Mounjaro if you: Are under 18, are pregnant or breastfeeding, have a severe allergy to tirzepatide, or have untreated or severe gastroparesis. Use our free BMI calculator to check your personal BMI and understand your starting point for eligibility discussions with your GP.
---COL_J_NOTES--- [Note: COL_J naturally incorporates the BMI calculator reference and maintains the comparison angle by emphasizing individual suitability through prescriber assessment.]- 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 better than Wegovy for everyone?
No. Mounjaro showed slightly higher average weight loss in trials, but results vary greatly between individuals. Wegovy may suit some people better depending on health conditions, other medications, or side effect tolerance. Only a prescriber can assess which is appropriate for your circumstances after clinical evaluation.
Can I get Mounjaro on the NHS in the UK?
Potentially, but access is limited. NICE has approved tirzepatide for NHS specialist weight management services, but availability varies by region and waiting lists can be very long. Your GP can refer you to a tier 3 specialist weight management service if you meet criteria. Private prescribing via online clinical assessment is also available.
What's the main difference between Mounjaro and Wegovy mechanisms?
Mounjaro activates two hormone pathways (GIP and GLP-1), while Wegovy activates only one (GLP-1). The dual mechanism may help some people, but both medications work alongside reduced-calorie diet and increased physical activity. Neither is a standalone solution.
Do I need a prescription to get Mounjaro in the UK?
Yes. Mounjaro is prescription-only and cannot be purchased without a valid UK prescription from a licensed prescriber. Following a clinical assessment, a prescriber will determine if you're eligible and if Mounjaro is the right choice for you compared to alternatives.
Can children take Mounjaro for weight management?
No. Mounjaro is only licensed for adults aged 18 and over in the UK. Children and young people should not take this medication. If you're concerned about a young person's weight, speak with their GP about age-appropriate support 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.