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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Ideal Body Weight Index — UK Health Guide
Your ideal body weight depends on your height, age, gender, and muscle mass — there's no single "perfect" number. In the UK, the NHS uses BMI (body mass index) as the primary tool to determine a healthy weight range, though this has important limitations. This guide explains what ideal body weight means in a UK context, how it's calculated, and what it means for your personal health.
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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.
Understanding Ideal Body Weight in the UK
Ideal body weight is a target weight range based on your height and build. The NHS defines a healthy weight as a BMI between 18.5 and 24.9, though for adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the threshold is lower (18.5 to 22.9) due to increased health risks at higher BMI levels. To calculate your ideal weight range, multiply your height in metres squared by 18.5 (lower bound) and 24.9 (upper bound). For example, at 1.73m (5ft 8in), a healthy weight falls between 55.4 kg (8st 10lbs) and 74.5 kg (11st 10lbs).
However, BMI has limitations — it doesn't account for muscle mass, bone density, or where fat is stored. An athletic person with significant muscle may have a higher BMI but lower body fat percentage. Your GP can provide personalised guidance on what a healthy weight means for you specifically, considering your individual health context, family history, and any existing health conditions.
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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.
UK Weight Management and NHS Resources
Rather than focusing on a single "ideal" number, the NHS emphasises weight management as part of overall health. Losing even 5–10% of your body weight can improve blood pressure, blood sugar control, and joint health. Use our free BMI calculator to find your current BMI and healthy weight range — this gives you a personalised target based on your height. For a practical overview of your weight in different units, the weight converter helps you switch between kg, stone, and pounds instantly. If you're considering weight loss, speak to your GP about options suited to your individual circumstances, including lifestyle changes, behaviour support, or prescription options if appropriate.
- 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's the difference between ideal body weight and healthy weight?
Ideal body weight is a target weight range based on height and BMI. Healthy weight means a weight at which your health risks are minimised. The NHS defines this as BMI 18.5–24.9 for most adults (lower for some ethnic groups). Your personal healthy weight depends on your build, muscle mass, and individual health context.
How is ideal body weight calculated in the UK?
The NHS uses BMI as the primary measure. Multiply your height in metres squared by 18.5 (lower bound) and 24.9 (upper bound) to find your healthy weight range. For example, at 1.70m, the range is approximately 53.5–71.9 kg. Our BMI calculator does this instantly for you.
Does ideal body weight apply to everyone?
No. BMI thresholds differ by age, sex, ethnicity, and muscle mass. Children use age-specific charts, not adult categories. The NHS recommends lower thresholds for South Asian, Chinese, and Black African populations. Very muscular individuals may need to assess body fat percentage alongside BMI.
What if I'm struggling to reach my ideal weight?
Contact your GP for personalised support. The NHS offers tier 1 (self-help), tier 2 (primary care programmes), and tier 3 (specialist weight management services). Your GP can discuss options suited to your health and circumstances, including behaviour change support and, where appropriate, prescription options.
Is there a "best" weight loss rate toward an ideal weight?
The NHS recommends losing 0.5–1 kg (1–2 lbs) per week as sustainable and safe. Faster weight loss is possible under medical supervision but increases muscle loss risk. Sustainable weight loss combines a modest calorie deficit with increased activity and behaviour change.
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.