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 Jab: NHS Eligibility and UK Prescribing
Mounjaro (tirzepatide) is a prescription-only weight management injection approved for use in the UK. If you're considering whether the Mounjaro jab might be suitable for you, understanding NHS eligibility criteria and how to access it through specialist services is essential. This guide explains NICE guidance, who qualifies, and how the NHS tier 3 pathway works — plus how this differs from private prescribing 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.
NHS Eligibility Criteria and NICE Guidance
NICE has approved tirzepatide (Mounjaro) for weight management within NHS specialist tier 3 services. Eligibility depends on both BMI and presence of weight-related health conditions.
- BMI of 30 kg/m² or above, OR
- BMI of 27–29.9 kg/m² with at least one weight-related health condition (type 2 diabetes, prediabetes, high blood pressure, high cholesterol, obstructive sleep apnoea, or cardiovascular disease)
- South Asian, Chinese, Black African, and Black Caribbean adults: lower thresholds apply (BMI 27.5 or above may qualify)
The Mounjaro KwikPen is a once-weekly pre-filled injection device, starting at 2.5 mg and escalating to a maximum of 15 mg per week. In clinical trials, tirzepatide helped participants lose an average of 15–21% of their body weight alongside reduced-calorie diet and increased physical activity. Individual results vary significantly. Use our free GLP-1 weight loss calculator above to explore projected outcomes at different doses.
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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 Access vs Private Route in the UK
NHS Access: Prescription through tier 3 specialist weight management services requires GP referral. NICE guidance emphasises tier 3 assessment, but waiting lists are very long in many regions — sometimes 6–12 months or longer. Availability varies by Integrated Care Board (ICB).
Private Access: Mounjaro is available through GPhC-registered online prescribing services following a clinical assessment. This route doesn't require NHS referral and typically offers faster access, but incurs direct costs (approximately £150–£320 monthly depending on dose). Both routes require a UK-licensed prescriber to assess suitability. Check your personal BMI and health context using our free BMI calculator to understand where you might sit within NHS eligibility guidelines.
- 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.
Am I eligible for Mounjaro through the NHS?
You may be eligible if your BMI is 30 or above, or 27–29.9 with a weight-related health condition (diabetes, high blood pressure, sleep apnoea, or cardiovascular disease). South Asian, Chinese, Black African, and Black Caribbean adults have lower thresholds. GP referral to tier 3 specialist services is required, and availability varies significantly by region.
How long does it take to access Mounjaro on the NHS?
Waiting times for NHS tier 3 specialist weight management services vary widely by region. Many areas have waiting lists of 6–12 months or longer. Private prescribing routes typically offer faster access but require direct payment.
What's the difference between Mounjaro and Wegovy for NHS prescribing?
Both tirzepatide (Mounjaro) and semaglutide (Wegovy) are approved by NICE for NHS specialist services. Mounjaro is a dual GIP and GLP-1 agonist; Wegovy is GLP-1 only. Clinical trial data showed slightly higher average weight loss with Mounjaro, though individual results vary. Availability depends on your local ICB.
Can I get the Mounjaro jab privately without NHS referral?
Yes. Private prescribing services assess your eligibility independently and can issue a prescription for Mounjaro if clinically appropriate. You'll pay directly (typically £150–£320 monthly depending on dose), and the prescription is dispensed by a GPhC-registered pharmacy.
What are the main side effects of the Mounjaro jab?
Very common side effects include nausea, diarrhoea, vomiting, constipation, and stomach pain — often mild and temporary during dose escalation. Less common side effects include injection site reactions, fatigue, and dizziness. Serious side effects (severe stomach pain, gallbladder problems, allergic reactions) are rare but require immediate medical attention. Always discuss side effect management with your prescriber.
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.