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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How to Work Out Your Percentage Weight Loss
Working out your percentage weight loss helps you track progress beyond just the number on the scales. Whether you're managing your weight through lifestyle changes alone or considering prescription options, understanding your percentage loss gives you meaningful context. This guide explains the calculation, shows you how to track progress effectively, and covers UK-licensed weight management medication available to eligible adults.
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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 Calculate Percentage Weight Loss
Percentage weight loss = (Starting weight – Current weight) ÷ Starting weight × 100
For example: If you started at 100 kg and now weigh 90 kg, your percentage loss is (100 – 90) ÷ 100 × 100 = 10%.
Why track percentage? Because a 5 kg loss means something different to a person starting at 70 kg versus 120 kg. In percentage terms, you can compare progress fairly regardless of starting weight.
- 5–10% loss = significant health improvements (blood pressure, blood sugar, joint pain)
- 10–15% loss = substantial cardiovascular and metabolic benefits
- 15%+ loss = major risk reduction for type 2 diabetes and heart disease
The NHS recommends losing 0.5–1 kg per week for sustainable weight management in the UK. Track your progress using our free progress tracker to monitor both kg lost and percentage improvement over time.
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.
UK Weight Loss Medication and NHS Options
If you're interested in prescription weight loss medication, three options are licensed in the UK: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are prescription-only medicines available to adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure.
NHS access: Available through tier 3 specialist weight management services (referral from your GP). Waiting lists vary by region.
Private access: Available through GPhC-registered online prescribers following a clinical assessment.
All weight loss medication works alongside dietary changes and increased physical activity — not instead of them. Talk to your GP about which option might suit you. Use our free BMI calculator to check your current BMI and understand your eligibility.
- 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 percentage weight loss is healthy?
The NHS recommends losing 0.5–1 kg per week, which typically represents 0.5–1% of body weight weekly. Even 5–10% loss brings measurable health benefits. Weight loss should be gradual and sustainable — faster loss increases muscle loss risk. Your GP can advise on a safe target for your circumstances.
How do I work out percentage weight loss in stone and pounds?
Convert to kg first (or use our free weight converter), then apply the formula: (starting weight – current weight) ÷ starting weight × 100. For example: starting at 100 kg (15st 10lbs), now 90 kg (14st 3lbs) = 10% loss. Tracking in kg is simpler mathematically, though the percentage itself is the same regardless of units.
Can prescription weight loss injections help me reach my percentage goal?
Yes. GLP-1 medications (Wegovy) and GIP/GLP-1 medications (Mounjaro) may help eligible adults lose 14–21% of body weight alongside diet and exercise, based on clinical trials. Individual results vary significantly. Your prescriber will discuss realistic targets and monitor your progress at regular appointments.
How often should I recalculate my percentage weight loss?
Weekly weigh-ins help you spot trends, though weight naturally fluctuates day-to-day due to hydration, hormones, and digestion. Calculate your percentage loss weekly or monthly depending on what motivates you. Our free progress tracker logs both actual weight and percentage automatically, making it easy to visualise your journey.
What's the difference between losing kg and losing a percentage?
Losing 10 kg means the same absolute loss regardless of starting weight — but it represents 10% loss for someone at 100 kg but only 5% for someone at 200 kg. Percentage loss is more meaningful because it reflects your individual progress. Both metrics matter: absolute loss for motivation, percentage for health context.
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.