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 is the Age Limit for Mounjaro in the UK?
Mounjaro (tirzepatide) is only prescribed to adults aged 18 and over in the UK. There is no upper age limit, but eligibility depends on BMI, weight-related health conditions, and clinical assessment. NHS prescribing follows NICE guidance, and access is typically through specialist tier 3 weight management services. This guide explains UK age requirements, NHS eligibility criteria, and how to access Mounjaro through the NHS or private prescription routes.
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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.
Age Limits and NHS Eligibility for Mounjaro
Minimum age: Mounjaro is not approved for anyone under 18 years old in the UK. The MHRA (Medicines and Healthcare products Regulatory Agency) has only licensed tirzepatide for use in adults aged 18 and above.
No maximum age: There is no upper age limit for Mounjaro, though prescribers assess suitability individually based on overall health, kidney function, and any existing conditions.
To be eligible for Mounjaro on the NHS in the UK, you must also meet BMI criteria: a BMI of 30 kg/m² or above, or BMI of 27–29.9 kg/m² with at least one weight-related health condition such as type 2 diabetes, high blood pressure, or cardiovascular disease. For South Asian, Chinese, Black African, or Black Caribbean adults, lower thresholds may apply (BMI 27.5 and above). Your GP can assess whether you meet eligibility criteria and refer you to a specialist tier 3 weight management service where Mounjaro may be prescribed.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
NHS vs Private Routes for Mounjaro Access
NHS route: Adults meeting BMI and health condition criteria can be referred by their GP to specialist tier 3 weight management services. NICE has approved tirzepatide for use within the NHS, but regional availability and waiting lists vary significantly. Some areas have several-month delays; others have very limited access. NHS prescription is typically free once approved.
Private route: Adults aged 18+ can access Mounjaro through private online prescribing without a GP referral, following an online clinical assessment by a UK-licensed prescriber. This route is faster but involves a private cost (approximately £129–£320+ per month depending on dose). Use our free GLP-1 weight loss calculator to estimate potential results at different tirzepatide doses.
If you're considering Mounjaro, calculate your BMI using our free BMI calculator to check whether you may meet NHS eligibility thresholds. Individual prescribing decisions are always based on clinical assessment, medical history, and current kidney and thyroid function.
- 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 there an age limit for Mounjaro in the UK?
Yes. Mounjaro is only prescribed to adults aged 18 and over in the UK. The MHRA has not approved tirzepatide for anyone under 18. There is no upper age limit, but prescribers assess suitability based on individual health status, kidney function, and any existing medical conditions.
Can a teenager get Mounjaro on the NHS?
No. Mounjaro is not approved for use in anyone under 18 in the UK. Young people with obesity are managed through NHS tier 1–3 services with lifestyle support, behavioural interventions, and specialist assessment — but weight loss medications like tirzepatide are not offered to under-18s.
What are the NHS eligibility criteria for Mounjaro?
You must be aged 18+, have a BMI of 30 kg/m² or above (or 27+ with weight-related health conditions), and be referred to a specialist tier 3 weight management service by your GP. Conditions that qualify include type 2 diabetes, prediabetes, high blood pressure, abnormal blood fats, sleep apnoea, and cardiovascular disease history.
How long do you have to wait for Mounjaro on the NHS?
Waiting times vary significantly by region and local integrated care board (ICB) capacity. Some areas have waits of several months; others have limited or no Mounjaro availability. Your GP can tell you about waiting times in your area when referring you to tier 3 services.
Can I get Mounjaro privately if I'm under 18?
No. Mounjaro cannot be prescribed to anyone under 18, whether through the NHS or private prescribing. The MHRA restriction applies across all UK prescribing routes. Under-18s should speak with their GP about age-appropriate weight management support.
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.