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 Does a BMI of 38 Mean in the UK?
A BMI of 38 falls into the obese category according to NHS guidelines, specifically Class II obesity (BMI 35–39.9). This means your weight carries increased health risks that merit professional support. The good news is that the NHS offers free weight management services, and even modest weight loss of 5–10% can significantly improve your health. Understanding where you stand on the BMI scale is the first step toward taking action. Use our free BMI calculator above to confirm your personal BMI and explore what the NHS recommends for your situation.
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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 What BMI 38 Means
According to NHS guidance, BMI 38 places you in the obese class II category (BMI 35.0–39.9). The full NHS BMI range UK includes: underweight (below 18.5), healthy weight (18.5–24.9), overweight (25.0–29.9), obese class I (30.0–34.9), obese class II (35.0–39.9), and severely obese (40.0+).
At BMI 38, your weight is significantly above the healthy BMI range. This increases your risk of type 2 diabetes, heart disease, high blood pressure, and certain cancers. However, the NHS recognises that obesity is a health condition that can be managed with appropriate support.
If you have South Asian, Chinese, Black African, or Black Caribbean heritage, NHS guidelines recommend lower thresholds — your risk profile may be higher at the same BMI. Use our weight converter to understand your weight in different units, then calculate your precise BMI using the calculator on this page.
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 Weight Management Support and Your Next Steps
The NHS offers a four-tier weight management pathway. At BMI 38, you may be eligible for tier 3 specialist weight management services through your GP. These services include structured diet and exercise programmes, behaviour change support, and where appropriate, prescription weight loss medications approved by NICE.
Contact your GP to discuss weight management support — they can refer you to local services or explore options with you. The NHS does not charge for these services. Your GP may also check for weight-related health conditions like type 2 diabetes or high blood pressure, which can inform your treatment plan. Even a 5–clinically studied weight loss can meaningfully improve your health outcomes.
- 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 a BMI of 38 dangerous?
A BMI of 38 indicates class II obesity and carries increased health risks including type 2 diabetes, heart disease, and high blood pressure. However, this is manageable through weight loss and lifestyle changes. The NHS provides free support to help you reduce these risks.
How much weight do I need to lose to improve my health?
Evidence suggests that losing just 5–10% of your body weight can meaningfully improve blood pressure, blood sugar control, and reduce joint strain. You don't need to reach a "healthy BMI" to see health benefits — every kilogram lost helps.
What does the NHS offer for someone with BMI 38?
Your GP can refer you to tier 3 specialist weight management services, which provide structured programmes, dietitian support, exercise advice, and behaviour change coaching. If appropriate, prescription weight loss medications may be discussed after assessment.
How accurate is BMI as a health measure?
BMI is a useful screening tool but has limitations — it doesn't distinguish between muscle and fat, doesn't account for where fat is stored, and doesn't measure overall fitness. Your GP will consider BMI alongside other factors like waist circumference and health conditions.
Can I access weight loss injections on the NHS with a BMI of 38?
Possibly. GLP-1 medications like Mounjaro and Wegovy are available through NHS tier 3 specialist services for eligible patients. Availability and waiting times vary significantly by region. Your GP can advise whether you might qualify and how to access them in your area.
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.