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 Much Weight Should You Lose Per Week?
The NHS recommends losing weight at a rate of 0.5 to 1 kilogramme (approximately 1 to 2 pounds) per week for safe and sustainable results. This target suits most adults aiming for long-term weight management without losing muscle mass or experiencing nutritional deficiencies. Weight loss speed depends on your starting weight, metabolism, diet quality, and physical activity level. Using our free weight converter and BMI calculator, you can establish your baseline and track realistic progress week by week.
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.
NHS Safe Weight Loss Rate and How It Works
A safe weight loss rate of 0.5–1 kg per week typically requires a calorie deficit of approximately 500 kcal per day. This means consuming 500 fewer calories than your body burns daily, which creates a deficit of 3,500 kcal per week — roughly equivalent to 0.5 kg of body fat lost.
- Faster loss (1.5+ kg/week) increases risk of muscle loss, nutrient deficiency, and gallstones — only recommended under medical supervision
- Very low calorie diets (below 800 kcal/day) require GP oversight and are typically used in specialist weight management services
- Individual variation is significant; some people lose faster initially due to water weight, then plateau
- Sustainable approach combines modest calorie reduction (diet) with increased physical activity (exercise)
Track your actual progress using our free progress tracker to identify your personal weight loss pattern over weeks and months.
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 Weight Loss Rate
Your weight loss speed depends on multiple factors including starting weight (heavier individuals often lose faster initially), age (metabolism slows with age), sex (men typically lose faster than women due to higher muscle mass), muscle mass (muscle burns more calories at rest), and medical conditions (thyroid disorders, PCOS, diabetes affect metabolism). Ethnicity also matters — UK adults of South Asian, Black African, Caribbean, or Chinese heritage may have different metabolic responses. Use the BMI calculator on this page to establish your healthy weight range for your height, then work backwards to set realistic weekly targets over 12–24 weeks.
- 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 losing 1kg per week safe?
Yes, the NHS considers 0.5–1 kg per week safe for most adults. Losing exactly 1 kg weekly is sustainable and shouldn't cause muscle loss if you include resistance exercise and adequate protein. Faster loss (over 1.5 kg/week) increases risks and should only occur under medical supervision.
Why do I lose weight faster in week one?
Initial rapid loss is mostly water weight, not fat. When you reduce calories or carbohydrates, your body uses stored glycogen (which holds water). Expect this to stabilise after week 1–2, then fat loss becomes the primary weight change. This is normal and does not mean your weight loss effort has failed.
What's the average weight loss on weight loss injections?
GLP-1 medications like Wegovy show average weight loss of around 14–15% of body weight over 68 weeks in clinical trials. Dual GIP/GLP-1 medications like Mounjaro show 15–21% average loss. Individual results vary significantly. Results require sustained use alongside reduced-calorie diet and physical activity.
How do I calculate my personalised weight loss target?
Determine your healthy weight range using the NHS BMI calculator (BMI 18.5–24.9). Subtract your current weight from your upper target weight, then divide by weeks available. For example: support gradual weight management = 0.5 kg/week. Use our free progress tracker to monitor weekly results and adjust as needed.
Should I aim for faster weight loss if I need to lose a lot?
No. Even if you need to lose 20+ kg, the NHS advises maintaining the 0.5–1 kg weekly rate for safety and sustainability. Faster loss increases muscle loss, nutrient deficiency risk, and weight regain likelihood. Speak to your GP about specialist support if you have a very high BMI or weight-related health conditions.
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.