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
Is Losing 1kg a Week Safe for Weight Loss?
Losing 1kg (approximately 2.2 lbs or 2st 3lbs) per week is at the upper end of what the NHS considers safe and sustainable weight loss. While it's achievable, it requires significant commitment to both diet and exercise. This guide explains what 1kg weekly loss means for your health, how to calculate whether it's realistic for you, and when prescription weight loss medication or NHS support might help accelerate results safely.
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.
What Does 1kg a Week Weight Loss Mean?
Losing 1kg per week typically requires a calorie deficit of approximately 7,000 calories over seven days, or around 1,000 calories per day. This is a significant deficit — the average UK adult woman consumes around 2,000 calories daily, and the average man around 2,500 calories daily. Achieving a 1,000-calorie deficit through diet alone would mean eating only 1,000–1,500 calories per day, which is below recommended intakes and should only be done under medical supervision.
Most people achieve 1kg weekly loss through a combination of reduced calorie intake and increased physical activity. For example, a 500-calorie dietary reduction plus 500 calories burned through exercise equals your 1,000-calorie daily deficit. This approach is more sustainable and preserves muscle mass better than severe dietary restriction alone.
- Sustainable approach: 500 kcal diet reduction + 500 kcal exercise = 1kg/week loss
- Requires consistency 7 days per week
- At upper limit of NHS safe weight loss recommendations
- Individual results vary based on metabolism, starting weight, and adherence
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.
NHS Guidelines and When to Seek Medical Support
The NHS recommends losing weight at a rate of 0.5 to 1kg per week as the safest, most sustainable approach. Losing 1kg weekly is safe for most adults but sits at the upper boundary — faster loss increases risk of muscle loss, nutritional deficiency, and reduced adherence over time. Check your personal BMI using our free BMI calculator above to understand your starting point and healthy weight target, then track progress with our free progress tracker.
If you're struggling to achieve weight loss through diet and exercise alone, or have a BMI of 30 or above (or 27+ with weight-related health conditions), your GP can refer you to NHS weight management services. Prescription weight loss medication like GLP-1 injections may support faster results alongside lifestyle changes. Our GLP-1 weight loss calculator can help estimate potential outcomes with medical support, though individual results always vary significantly.
If you have type 2 diabetes, prediabetes, high blood pressure, or other weight-related health conditions, losing even 5–10% of your body weight can meaningfully improve health markers. A 1kg-per-week loss reaches clinically studied weight loss in 10 weeks for someone starting at 100kg — a significant milestone. However, very gradual weight management can trigger gallbladder problems and other complications in some people. Always consult your GP before starting an intensive weight loss programme, especially if you take any medications or have existing health conditions.
- 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 1kg a week weight loss too fast?
Not necessarily. The NHS considers 0.5–1kg per week safe for most adults. Losing 1kg weekly sits at the upper limit but is achievable with consistent calorie deficit and exercise. Faster loss (>1.5kg/week) without medical supervision is not recommended, as it increases muscle loss and nutrient deficiency risk.
How many calories do I need to cut to lose 1kg per week?
You need a total deficit of approximately 7,000 calories per week, or 1,000 calories per day. Most people achieve this through 500 kcal diet reduction plus 500 kcal from exercise, rather than extreme dietary restriction alone, which is more sustainable.
Can I lose 1kg a week on GLP-1 medication like Wegovy?
GLP-1 medications like Wegovy may support faster weight loss than diet and exercise alone. Clinical trials showed average weight loss of approximately 15% body weight over 68 weeks — roughly 0.4–0.5kg per week on average. Some individuals lose more rapidly, others more slowly. Results vary significantly and always require lifestyle changes alongside medication.
What's the difference between losing 1kg a week and the NHS recommendation?
The NHS recommends 0.5–1kg per week. Losing exactly 1kg weekly is safe but leaves little margin for fluctuation. Aiming for 0.5–0.75kg per week is often more sustainable, especially long-term, as it's easier to maintain and reduces risk of muscle loss and nutritional deficiency.
When should I see my GP about weight loss?
See your GP if you're struggling to lose weight through diet and exercise, have a BMI of 30 or above, have weight-related health conditions, or want personalised advice. Your GP can refer you to NHS weight management services or discuss whether prescription weight loss medication is appropriate for you.
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.