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 Is a Healthy Weight Loss Rate?
The NHS recommends losing weight at a rate of 0.5 to 1 kg (1 to 2 lbs) per week for sustainable, safe weight loss. This might sound slow, but it's the evidence-based approach backed by health organisations worldwide. Faster weight loss is possible, especially with medical support, but it comes with greater risks including muscle loss, nutritional deficiencies, and metabolic adaptation. Understanding the healthy weight loss rate helps you set realistic goals and maintain progress long-term without damaging your health.
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.
How Weight Loss Rate Works — The Science
A healthy weight loss rate is achieved through a calorie deficit of approximately 500 kcal per day, which typically results in losing around 0.5 kg per week. To lose 1 kg per week, you'd need a deficit of roughly 1,000 kcal daily — substantial but achievable for many people through combined dietary changes and increased physical activity.
- Moderate deficit (500 kcal/day): ~0.5 kg/week loss, preserves muscle mass, sustainable long-term
- Larger deficit (1,000 kcal/day): ~1 kg/week loss, requires careful nutrition and medical support if extended
- Very low calorie diet (below 800 kcal/day): Only under medical supervision, typically short-term
Use our free BMI calculator to check your current healthy weight range for your height, then our GLP-1 weight loss calculator can help project realistic timelines based on your personal situation.
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.
Factors Affecting Your Ideal Weight Loss Rate
Individual weight loss varies based on starting weight, age, sex, muscle mass, metabolism, and medical conditions. Someone with a higher starting weight may lose faster initially (water loss), whilst someone with low muscle mass may lose more slowly. Medical factors like thyroid function, diabetes, and PCOS affect metabolism. Age matters too — metabolic rate generally declines with age, so older adults may lose weight more slowly. Frame size and ethnicity also influence ideal body weight range — the NHS provides lower BMI thresholds for South Asian, Chinese, Black African, and Black Caribbean adults due to higher health risks at lower weights. Track progress with our free progress tracker to monitor your individual rate beyond just the scale.
- 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 1 kg per week weight loss safe?
Yes, 1 kg per week is within NHS safe guidelines. This requires a 1,000 kcal daily deficit through diet and exercise combined. It's sustainable for most people but may require professional support. Faster rates increase risks of muscle loss and nutritional deficiency.
Why is slow weight loss better than fast weight loss?
Slow weight loss (0.5–1 kg/week) preserves muscle mass, improves adherence, and creates sustainable habits. Rapid loss (over 1.5 kg/week) causes more muscle loss, increases fatigue, and often leads to rebound weight gain. Sustainable weight loss lasts longer.
How can I calculate my own calorie deficit?
Estimate your daily calorie needs (varies by age, sex, activity level), then subtract 500 kcal for 0.5 kg loss or 1,000 kcal for 1 kg loss per week. Use an online TDEE calculator or consult your GP for personalised guidance. Our BMI calculator helps establish your healthy weight range first.
Does weight loss medication change the healthy rate?
GLP-1 medications like Mounjaro or Wegovy may increase weight loss rate to 1–2 kg per week because they reduce appetite and support calorie deficit more easily. Results vary individually. Medical supervision is essential to monitor safety and nutrition.
What if I'm losing weight faster than 1 kg per week?
Initial rapid loss (first 1–2 weeks) is often water loss, not fat — this is normal. If you're consistently losing over 1.5 kg weekly, discuss with your GP to ensure adequate nutrition and muscle preservation. Adjust diet and activity as needed.
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.