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
What BMI Do You Need for Mounjaro Under NHS Guidance?
In the UK, adults with a BMI of 30 or above, or 27 or above with weight-related health conditions, may be eligible for Mounjaro (tirzepatide) through NHS specialist weight management services. However, eligibility varies by region and depends on individual health circumstances. The NHS uses specific BMI thresholds alongside other health factors to determine whether prescription weight loss treatment is appropriate. Understanding where your BMI falls within NHS categories is the first step towards accessing support. Use our free BMI calculator above to find your personal BMI instantly.
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Calculate Your BMI Instantly
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 BMI Categories and Mounjaro Eligibility Thresholds
The NHS BMI categories are the standard framework used across UK health services. A healthy BMI ranges from 18.5 to 24.9, overweight is 25.0 to 29.9, and obese is 30.0 and above. For Mounjaro eligibility, you typically need a BMI of 30 or higher, or a BMI between 27 and 29.9 if you have weight-related health conditions such as type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease.
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower BMI thresholds due to higher health risks at lower weights. In these cases, eligibility may start at a BMI of 27.5 or above. Your GP or a specialist prescriber will assess your individual situation using the full BMI formula and your health history, not BMI alone.
- BMI 18.5–24.9: Healthy weight
- BMI 25.0–29.9: Overweight
- BMI 30.0+: Obese (eligible for Mounjaro consideration)
- BMI 27–29.9 with health conditions: May be eligible
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.
How the NHS Assesses You for Weight Management Treatment
The NHS follows a structured pathway called the weight management tier system. Most adults start at tier 1 with lifestyle support and digital tools, then tier 2 with primary care intervention. For prescription medications like Mounjaro, you're referred to tier 3 or tier 4 specialist weight management services. A prescriber will evaluate your BMI, health conditions, previous weight loss attempts, and medication interactions before offering treatment.
Access through the NHS can involve waiting lists in many regions. Alternatively, you can access Mounjaro through private online prescribing following a clinical assessment from a UK-licensed prescriber. Either route requires confirmation that you meet eligibility criteria and are suitable for GLP-1 treatment. Track your progress with our free progress tracker once you begin any weight management programme.
- 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 is the minimum BMI to be prescribed Mounjaro on the NHS?
Generally, a BMI of 30 or above qualifies you for Mounjaro consideration on the NHS. However, if you have weight-related health conditions such as type 2 diabetes or high blood pressure, you may be eligible with a BMI between 27 and 29.9. For people of South Asian or Black African heritage, lower thresholds apply — starting at around 27.5.
Does BMI alone determine Mounjaro eligibility?
No, BMI is just one factor. The NHS also considers your health conditions, previous weight loss attempts, current medications, and overall health status. A prescriber will assess the full picture, not BMI in isolation, to determine if Mounjaro is suitable for you.
How do I calculate my BMI to check Mounjaro eligibility?
Use the BMI formula: weight (kg) divided by height (m) squared. Or use our free BMI calculator above to find your BMI instantly. For example, someone weighing 85kg and 1.75m tall has a BMI of approximately 27.8. You can also convert between kg, stone, and pounds using our weight converter.
Are BMI thresholds for Mounjaro different for different ethnic backgrounds?
Yes. The NHS recognises that South Asian, Chinese, Black African, and Black Caribbean adults face higher health risks at lower BMI levels. Lower thresholds apply to these groups — typically starting at BMI 27.5 rather than 30 — to provide earlier intervention and support.
What happens if my BMI is below 27 but I have serious health problems?
If you have significant health conditions related to weight, speak to your GP. While you may fall below standard BMI thresholds, your GP can assess your individual circumstances and refer you to specialist services if appropriate. Health factors beyond BMI matter in clinical decisions.
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.