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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Mounjaro Prescribing Guidelines in the UK
Mounjaro (tirzepatide) is a prescription-only weight loss injection licensed in the UK for adults meeting specific eligibility criteria. Whether you can access Mounjaro depends on your BMI, health conditions, and whether you pursue NHS or private prescribing routes. This guide explains UK prescribing guidelines, who qualifies, and how to get assessed for this weight loss treatment. Use our free BMI calculator above to check where you stand against UK eligibility thresholds.
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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.
UK Eligibility Criteria for Mounjaro
In the UK, Mounjaro may be prescribed to adults who meet at least one of these criteria: a BMI of 30 kg/m² or above (obesity), or a BMI of 27–29.9 kg/m² (overweight) alongside at least one weight-related health condition.
Weight-related conditions that may qualify include type 2 diabetes, prediabetes, high blood pressure, abnormal blood fats (dyslipidaemia), obstructive sleep apnoea, or a history of heart attack or stroke.
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower BMI thresholds due to higher cardiovascular and metabolic risk at lower weights. Eligibility may begin at BMI 27.5 or above for these groups.
Patients must be 18 or older, not pregnant or breastfeeding, and have no contraindications (severe gastroparesis, untreated thyroid cancer, severe kidney disease).
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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.
NHS vs Private Prescribing Routes
NHS access: Mounjaro prescriptions through the NHS are issued by specialist tier 3 and tier 4 weight management services, not by GPs. You'll need a GP referral to these services, though availability and waiting times vary significantly across UK regions. Some areas have substantial waiting lists.
Private access: Mounjaro is available through private UK-licensed prescribers following an online consultation and clinical assessment. This route does not require NHS referral and allows faster access, though there is a cost (typically £129–£320 per month depending on dose and provider).
Both routes require a clinical assessment to confirm eligibility and suitability before a prescription is issued. A prescriber will review your medical history, current medications, and health conditions.
Dose titration: Mounjaro is started at a low dose (2.5 mg once weekly) and typically increased every 4 weeks, with doses progressing to 5 mg, 7.5 mg, 10 mg, 12.5 mg, and up to 15 mg maximum. Each KwikPen contains 4 weekly doses. Prescribers adjust based on tolerance and response.
Monitoring: Patients typically have regular check-ins with their prescriber to discuss side effects, weight loss progress, and any medication adjustments needed. Try our GLP-1 weight loss calculator to estimate potential outcomes at different doses based on clinical trial data.
Important: Mounjaro is most effective alongside a reduced-calorie diet and increased physical activity—prescription treatment is not a standalone solution.
- 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.
Can I get Mounjaro on the NHS?
Yes, Mounjaro is approved by NICE for NHS use, but access is through specialist tier 3/4 weight management services, not standard GP prescriptions. You'll need a GP referral, and availability varies significantly by region. Waiting lists can be lengthy in some areas.
What BMI do I need to be eligible for Mounjaro in the UK?
You generally need a BMI of 30 or above, or 27–29.9 with a weight-related health condition (diabetes, high blood pressure, sleep apnoea, etc.). For South Asian, Chinese, Black African, or Black Caribbean adults, lower thresholds may apply. Use our BMI calculator to check your personal BMI.
How is Mounjaro prescribed—what's the starting dose?
Mounjaro starts at 2.5 mg once weekly and typically increases by 2.5 mg every 4 weeks up to a maximum of 15 mg weekly. Your prescriber adjusts based on your tolerance and response. Each KwikPen has 4 doses.
What's the difference between NHS and private Mounjaro prescribing in the UK?
NHS prescriptions come through specialist weight management services (longer wait, free on prescription). Private prescriptions come from UK-licensed online prescribers following a consultation (faster access, cost applies). Both require clinical assessment.
How does Mounjaro compare to Wegovy for UK prescribing?
Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist; Wegovy (semaglutide) is GLP-1 only. Both are prescription-only and have similar BMI eligibility thresholds. Mounjaro tends to show slightly higher average weight loss in trials, but individual results vary significantly. Your prescriber will assess which suits you.
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.