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 GP Criteria: UK Eligibility Requirements
If you're considering Mounjaro (tirzepatide) for weight management in the UK, your GP will assess your eligibility based on specific criteria. These criteria include your BMI, existing health conditions, and whether you meet NHS thresholds for specialist referral. Understanding what your GP will look for helps you prepare for a conversation about whether this prescription-only injection is appropriate for you.
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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.
BMI Thresholds and Health Condition Requirements
Your GP will assess your eligibility for Mounjaro using two main criteria: your BMI (body mass index) and whether you have weight-related health conditions. According to NHS guidance, you may be eligible if you have 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 you include type 2 diabetes or prediabetes, high blood pressure (hypertension), abnormal blood cholesterol or triglycerides (dyslipidaemia), obstructive sleep apnoea, or a history of heart attack, stroke, or other cardiovascular disease. Your GP will also consider your age, medical history, medications, and whether you've tried other weight loss methods. Check your personal BMI using our free BMI calculator above — this will help you understand where you stand against these thresholds.
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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.
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Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Ethnicity-Adjusted Criteria and NHS Referral Routes
Important: If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, your GP may apply lower BMI thresholds. The NHS recognises that these groups face higher health risks at lower BMI levels — eligibility may begin at a BMI of 27.5 or above. This is evidence-based and reflects your group's increased vulnerability to type 2 diabetes and cardiovascular disease.
Access to Mounjaro through the NHS requires a referral to a specialist tier 3 weight management service — your GP cannot prescribe it directly in most cases. This means a waiting list may apply, and availability varies significantly by region. Private access is available through UK-licensed prescribers without NHS referral, though this involves a cost.
Contraindications matter too: Your GP will screen for reasons you cannot take Mounjaro. These include pregnancy or plans to become pregnant, breastfeeding, severe stomach problems, a personal or family history of thyroid cancer, or an allergy to tirzepatide. Your prescriber will also assess your current medications — Mounjaro can affect how oral contraceptives and some diabetes medications work, so adjustments may be needed.
- 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.
What BMI do I need to ask my GP about Mounjaro?
The NHS threshold is a BMI of 30 or above (obesity), or 27–29.9 with at least one weight-related health condition like type 2 diabetes, high blood pressure, or sleep apnoea. If you're of South Asian, Chinese, Black African, or Black Caribbean heritage, lower thresholds may apply (from BMI 27.5+). Use our free BMI calculator to check yours instantly.
Can my GP prescribe Mounjaro directly, or do I need a referral?
In most cases, your GP will refer you to a specialist tier 3 weight management service, where a specialist team assesses and prescribes Mounjaro if appropriate. NHS prescription is not available directly from general practice. Private prescribing is available through online UK-licensed prescribers without referral.
Will my GP reject me for Mounjaro if I have type 2 diabetes?
No — having type 2 diabetes actually strengthens your eligibility, as it's a weight-related health condition. However, your GP will need to assess your diabetes medications and may need to adjust them, as Mounjaro can affect blood sugar control. Your prescriber will work with you to ensure safe combined use.
How long does a GP assessment for Mounjaro eligibility take?
A GP appointment to discuss eligibility typically takes 15–20 minutes. Your GP will review your BMI, medical history, medications, and health conditions. If you meet criteria, they'll issue a referral to specialist services. NHS referral-to-treatment times for tier 3 services vary widely by region — often several months.
What happens if I don't meet my GP's criteria for Mounjaro?
If you don't meet NHS criteria, your GP may suggest alternative approaches: lifestyle support, NHS weight loss programmes (like the NHS Weight Loss Plan), tier 2 community services, or other evidence-based options. You can discuss private options, though these require personal cost. Your GP can advise what's most appropriate for your situation.
Ready to take control of your weight loss journey?
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