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 Causes gradual weight management?
gradual weight management can happen for many reasons — some healthy, some concerning. Understanding the causes helps you identify whether your weight loss is safe and sustainable. Common causes include intentional calorie restriction, increased physical activity, prescription weight loss medication, or underlying medical conditions. Some people experience gradual weight management when starting GLP-1 weight loss injections or other prescription treatments. If you've noticed sudden weight changes, it's important to understand what's driving them and whether you should speak to your GP. Use our free BMI calculator to track where your weight sits on NHS health ranges.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
Intentional Weight Loss vs Unintentional Changes
Intentional gradual weight management typically happens when you make deliberate lifestyle changes or use prescription weight loss medication. The NHS recommends losing 0.5 to 1 kg per week for sustainable results — faster loss is possible but requires medical oversight. With GLP-1 weight loss injections like Wegovy (semaglutide), clinical trials showed participants lost an average of 15% of body weight, though individual results vary significantly. This medication works by reducing appetite and helping you feel fuller after smaller meals, supporting meaningful weight management alongside dietary changes.
Unintentional gradual weight management — losing weight without trying — can indicate an underlying health issue. Causes include thyroid problems, diabetes, infections, stress, or certain medications. If you're losing weight unexpectedly, contact your GP for assessment. They can run blood tests and provide personalised advice based on your health history.
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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.
Safe Weight Loss and When to Seek Help
The NHS emphasises that safe, sustainable weight loss involves both dietary changes and increased physical activity. Very gradual weight management (more than 1.5 kg per week without medical supervision) can lead to muscle loss, nutritional deficiencies, and gallstones. If you're considering prescription weight loss medication for rapid results, a licensed prescriber will assess your eligibility through a clinical evaluation — these medications are prescription-only and require individual assessment.
Track your progress safely using our free progress tracker. Contact your GP if you experience unexplained gradual weight management, as this may indicate a medical condition requiring investigation. For weight management in the UK, NHS weight loss services and prescription options are available through specialist tier 3 services or private prescribing pathways.
- 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 gradual weight management dangerous?
gradual weight management above 1.5 kg per week without medical supervision can cause muscle loss, nutrient deficiencies, and gallstones. The NHS recommends 0.5 to 1 kg per week as safe and sustainable. Faster loss requires medical oversight and should only happen under professional guidance.
Why do GLP-1 injections cause gradual weight management initially?
GLP-1 medications like Wegovy work by reducing appetite, slowing stomach emptying, and helping you feel fuller. Many people eat significantly less naturally, leading to faster initial weight loss. Results vary individually — clinical trials showed average weight loss of around 15%, though some lose more or less.
Can I lose weight rapidly with prescription weight loss medication?
Prescription weight loss injections may support faster weight loss than diet alone — clinical evidence shows average losses of 15–21% body weight. However, these medications work alongside reduced-calorie diet and exercise, not instead of them. Individual results vary and require clinical assessment for eligibility.
What causes unintentional gradual weight management?
Unintentional weight loss can indicate thyroid disease, diabetes, infections, stress, depression, or certain medications. If you're losing weight without trying, contact your GP for blood tests and assessment. Rapid unexplained weight loss requires professional investigation.
How can I track safe weight loss progress?
Use our free progress tracker to log your weight and monitor trends over time. Check your BMI using our calculator to see where you sit on NHS health ranges. Aim for 0.5 to 1 kg per week — sustainable loss that protects muscle and nutritional health.
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.