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
How Do You Determine Weight in the UK?
Determining your weight involves more than just stepping on the scales. In the UK, healthcare professionals use several methods to assess whether your weight is healthy, including BMI calculations, waist measurements, and NHS health guidance. Understanding how weight is properly determined helps you make informed decisions about your health and whether you might benefit from weight management support. Our free BMI calculator and weight converter make it easy to check your personal metrics against NHS standards.
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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.
Methods Used to Determine Healthy Weight
BMI (Body Mass Index) is the most common method used by the NHS to determine whether a weight is healthy. BMI is calculated by dividing your weight in kilograms by your height in metres squared. According to NHS guidance, a healthy BMI falls between 18.5 and 24.9 for most adults. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds starting at 18.5 to 22.9, as these groups face higher health risks at lower BMI levels.
Waist circumference is equally important. The NHS states that for men, a waist over 94cm (37 inches) indicates increased health risk, while over 102cm (40 inches) indicates high risk. For women, measurements over 80cm (31.5 inches) and 88cm (34.5 inches) respectively indicate increased and high risk. This is because where fat is stored matters for your cardiovascular health.
Use our free weight converter above to check your weight in kg, stone, and pounds, then calculate your BMI using our BMI calculator to see where you fall on the NHS scale.
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.
Why Weight Alone Isn't Enough
Simply knowing your weight in kilograms or stone isn't enough to determine whether you're at a healthy weight. Two people of the same weight and height can have very different body compositions — one may be muscular whilst another carries more fat. This is why the NHS uses BMI as a screening tool, but also recommends considering waist measurement and overall health context.
Your GP can provide personalised health advice about what your weight means for you individually, taking into account your age, medical history, fitness level, and family background. If you're concerned about your weight or have weight-related health conditions like type 2 diabetes or high blood pressure, your GP can discuss weight management options with you, including referral to specialist services or discussion of suitable treatments.
- 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 a healthy weight range for my height in the UK?
The NHS defines healthy weight as a BMI between 18.5 and 24.9 for most adults. Your exact healthy weight range depends on your height. For example, at 5ft 8in (1.73m), the healthy weight range is approximately 55–74kg (8st 10lbs to 11st 10lbs). Use our free BMI calculator above to find your personalised healthy range, or speak to your GP for individual advice.
Why is waist measurement important alongside weight?
Waist circumference indicates where fat is stored on your body. Excess fat around the abdomen poses higher cardiovascular and metabolic risks than fat stored elsewhere. Even if your BMI is in the healthy range, a large waist circumference can indicate increased health risk. The NHS recommends measuring waist regularly alongside weight monitoring.
Does a higher weight always mean I'm unhealthy?
Not necessarily. BMI doesn't distinguish between muscle and fat — athletes may have high BMI but excellent health. Conversely, someone with a "healthy" BMI but high body fat percentage and poor fitness may face health risks. This is why the NHS considers BMI as one screening tool among several, including waist measurement, blood pressure, and blood sugar levels.
How often should I check my weight?
Weekly weigh-ins are common for weight management tracking, ideally on the same day and time of day, as weight naturally fluctuates with water retention and meals. However, daily weighing can be unhelpful as natural variation creates unnecessary anxiety. Monthly or quarterly assessments with your GP provide better context for long-term health trends.
Can I use BMI to check if I need weight management support?
BMI is a useful starting point. If your BMI is 30 or above, or 27–29 with weight-related health conditions (diabetes, high blood pressure, sleep apnoea), you may be eligible for NHS specialist weight management support or prescription weight management options. Use our free BMI calculator to check your BMI, then discuss options with your GP.
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.