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 Classed As gradual weight management?
gradual weight management is typically defined as losing more than 1 kg (2.2 lbs) per week, or roughly 4 kg per month. The NHS recommends a safer, sustainable rate of 0.5 to 1 kg per week for most adults. Losing weight faster than this can lead to muscle loss, nutritional deficiencies, fatigue, and gallstones. If you're considering weight management in the UK, understanding safe weight loss rates is essential before starting any diet or medication. Our free BMI calculator and weight converter can help you track your current weight in both metric and imperial measurements.
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.
Why gradual weight management Is Risky
gradual weight management—typically more than 1.5 kg per week without medical supervision—carries several health risks that make slower, sustained loss preferable for long-term success.
- Muscle loss: Fast weight loss often includes loss of lean muscle tissue, not just fat, reducing metabolism and strength
- Nutrient deficiencies: Very low-calorie diets (under 800 kcal/day) may lack essential vitamins, minerals, and protein
- Gallstones: Rapid loss increases risk of gallstone formation, which can cause severe abdominal pain
- Dehydration and fatigue: Quick weight reduction often involves fluid loss and can leave you exhausted
- Metabolic slowdown: Extreme calorie restriction may lower your metabolic rate, making weight regain more likely once you resume normal eating
- Hair loss and skin changes: Nutritional stress can cause temporary alopecia and loose skin
This is why NHS weight loss guidance emphasises a calorie deficit of around 500 kcal per day, which typically results in a safe 0.5 kg per week loss.
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.
Safe Weight Loss Rates and Medical Support
Safe rate: The NHS recommends losing 0.5 to 1 kg per week for sustainable results that preserve muscle and overall health. At this pace, you can expect to lose roughly 2–4 kg per month. Even a 5–10% reduction in your body weight can deliver meaningful health benefits, including improved blood pressure, better blood sugar control, and reduced joint strain.
If you're losing weight faster than 1.5 kg per week, or if you're following a very low-calorie diet, you should be under medical supervision. This is where prescription weight management options like GLP-1 medications may help—they support weight loss alongside dietary changes, allowing your GP or prescriber to monitor your progress. Use our GLP-1 weight loss calculator to explore potential outcomes with medical support, and our progress tracker to log your journey safely.
- 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 2 kg per week considered gradual weight management?
Yes, losing 2 kg (4.4 lbs) per week is above the NHS safe rate and would be classified as rapid. The recommended safe rate is 0.5–1 kg per week. Faster loss can lead to muscle loss, fatigue, and nutritional deficiencies. If you're losing this quickly, speak to your GP to ensure it's safe.
Can you lose weight rapidly with GLP-1 medications like Mounjaro or Wegovy?
Clinical trials show that GLP-1 medications support significant weight loss—Wegovy showed average loss of around 15% body weight in trials. However, this occurs over months with proper dosing and diet changes, not as rapid loss. Weight loss medications are prescription-only and work gradually alongside lifestyle changes.
What is the fastest safe weight loss rate?
Under medical supervision, you may achieve up to 1–1.5 kg per week safely, or faster under very low-calorie diet (VLCD) programmes in specialist settings. Without medical support, the NHS safe rate is 0.5–1 kg per week. Always consult your GP before pursuing gradual weight management.
What happens if you lose weight too quickly?
gradual weight management can cause muscle loss, gallstones, dehydration, nutrient deficiencies, hair loss, and metabolic slowdown. It's also often unsustainable—fast loss is frequently followed by rapid regain. Slower, sustained weight loss preserves muscle and is more likely to result in long-term success.
Does prescription weight loss medication cause gradual weight management?
Prescription medications like GLP-1 agonists support weight loss at a moderate to steady rate over weeks and months, not overnight. Individual results vary, and medication works alongside a reduced-calorie diet and increased physical activity. Your prescriber will monitor your progress to ensure safe, sustainable outcomes.
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.