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
Understanding Your Weight On The Scale
A weight reading on the scale is just one snapshot of your health. In the UK, we measure body weight in stone, pounds, and kilograms — and knowing how to interpret that number is important. Your weight fluctuates daily due to water retention, food intake, and hormonal changes, so a single scale reading doesn't tell the whole story. The NHS recommends looking at weight trends over weeks, not daily variations. This guide explains how to use scales effectively, understand your weight in UK measurements, and know whether your reading falls within a healthy weight range for your age and height.
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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.
How To Use Bathroom Scales Accurately
For consistent and reliable weight readings, follow these best practices: weigh yourself at the same time each day (ideally first thing in the morning before eating or drinking), use the same scales, and wear similar clothing each time. Place scales on a flat, hard surface — not carpet or tiles that slope — as uneven surfaces affect accuracy. Digital scales are generally more accurate than mechanical ones, but both can drift over time, so calibrate occasionally with a known weight.
- Weigh weekly rather than daily to avoid obsessing over natural fluctuations
- Track weight trends over 4–8 weeks to see real progress
- Remember that muscle is denser than fat — weight alone doesn't show body composition
- Use our free weight converter to switch between kg, stone, and lbs if needed
Weight changes of 1–2 kg in a day are usually water and food, not fat loss. The NHS recommends sustainable weight loss of 0.5–1 kg per week.
Clinically BackedWeight Loss
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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.
Healthy Weight Ranges In The UK
Your healthy weight depends on your height and age. The NHS uses BMI (Body Mass Index) as a screening tool: a healthy BMI is between 18.5 and 24.9. Try our free BMI calculator above to check where your current weight sits. For an adult 1.70m tall (5ft 7in), a healthy weight range is roughly 53–72 kg (8st 5lbs to 11st 4lbs).
Important: BMI has limitations — it doesn't account for muscle mass or where fat is stored. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower BMI thresholds (18.5–22.9 for healthy weight) due to higher health risks at standard thresholds. Your GP can give personalised advice about what your individual weight reading means for your health.
- 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 should my weight be in stone and pounds?
There's no single "right" weight — it depends on your height, age, and body composition. Use the healthy weight UK BMI range for your height (typically 18.5–24.9 BMI). Our BMI calculator shows your healthy range instantly. For personalised guidance, ask your GP, as they'll consider your full health picture.
Why does my weight fluctuate so much day-to-day?
Daily fluctuations of 1–2 kg are normal and are usually due to water retention, food intake, hormones (especially in women), or toilet habits — not fat loss. Track weekly or fortnightly trends instead. Weight loss of 0.5–1 kg per week is considered healthy and sustainable by the NHS.
Should I weigh myself every day?
The NHS recommends weighing weekly rather than daily to avoid obsessing over natural variations. Daily weighing can be discouraging and doesn't reflect true progress. Choose one day and time each week (ideally morning before eating) for consistency.
How accurate are bathroom scales?
Digital scales are generally more accurate than mechanical ones, but accuracy depends on proper placement (flat, hard surface) and calibration. Replace scales every 3–5 years as they can drift. For clinical measurements, your GP's scales are most reliable.
What's the difference between weight and BMI?
Weight is just a number; BMI factors in your height to estimate whether weight is healthy for you. BMI is a useful screening tool but has limitations — it doesn't distinguish muscle from fat. Use our free BMI calculator plus weight converter to get the full picture.
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.