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
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Is Losing 1kg Per Week Safe and Realistic?
Losing 1kg per week is a commonly discussed target for weight management in the UK, but whether it's realistic depends on your individual circumstances, starting weight, and the methods you use. The NHS recommends a sustainable weight loss rate of 0.5 to 1kg per week as a safe target for most adults. Achieving 1kg weekly loss typically requires a significant calorie deficit alongside lifestyle changes, and for some people, prescription weight loss medication may be part of a structured programme. This guide explains how 1kg per week weight loss works, whether it's achievable for you, and when to seek professional support.
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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 Much Calorie Deficit Creates 1kg Weekly Loss?
To lose 1kg of body weight, you need to create a calorie deficit of approximately 7,700 kcal — meaning you must consume or burn 7,700 kcal more than your body requires over a week. A 1kg weekly loss therefore requires an average deficit of about 1,100 kcal per day, which is significant for most people.
This can be achieved through:
- Diet alone: Reducing food intake by around 1,100 kcal daily (often challenging without professional support)
- Exercise alone: Burning 1,100 extra kcal daily through physical activity (difficult to sustain)
- Combined approach: A 500–600 kcal dietary reduction plus 500 kcal burned through exercise — this is more sustainable
- Medical support: Weight loss medications like GLP-1 injections (Wegovy, Mounjaro) reduce appetite, making calorie deficits easier to maintain alongside diet and exercise changes
Your starting weight, age, and metabolism all affect how quickly you lose weight. Heavier individuals typically lose weight faster initially than lighter individuals aiming for the same weekly loss.
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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.
Is 1kg Per Week Safe and Sustainable?
The NHS states that 0.5 to 1kg per week is a safe, sustainable rate for most adults following a combination of diet and exercise. Losing faster than 1kg weekly — without medical supervision — risks losing muscle alongside fat, which reduces metabolic rate and makes regaining weight more likely.
However, 1kg weekly loss is not realistic or necessary for everyone. Factors affecting achievability include:
- Your current BMI and starting weight (use our free BMI calculator to find your category)
- Medical conditions like hypothyroidism or PCOS, which slow metabolism
- Medications you take that affect weight
- Your lifestyle capacity for sustained calorie deficit and exercise
- Genetic and metabolic factors
For many people, aiming for 0.5kg weekly loss is more realistic and just as effective long-term. Even modest weight loss of 5–10% of body weight brings meaningful health benefits.
- 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.
Can I lose 1kg per week without exercise?
Theoretically yes — a 1,100 kcal daily dietary deficit alone would create 1kg weekly loss. However, the NHS recommends combining diet with physical activity for better long-term results, improved health outcomes, and to help preserve muscle mass. Exercise also supports mental health during weight loss.
Does GLP-1 weight loss medication help achieve 1kg per week loss?
GLP-1 medications like Wegovy and Mounjaro can support weight loss by reducing appetite and food cravings, making calorie deficits easier to maintain. In clinical trials, average weight loss ranged from 15–21% of body weight over several months — though individual results vary significantly and are influenced by diet, exercise, and personal factors.
How long would it take to lose 10kg at 1kg per week?
At a consistent 1kg weekly loss, losing 10kg would take approximately 10 weeks. However, weight loss is rarely linear — loss is typically faster in the first 2–4 weeks, then may plateau. Use our free progress tracker to monitor your weight loss journey and identify patterns.
Is 1kg per week realistic if I have a BMI over 35?
Faster initial weight loss (1–2kg per week) is sometimes realistic for people with higher BMI in the first 4–8 weeks, as they have a larger deficit capacity. However, this typically slows over time. Your GP or a weight management specialist can give you personalised targets based on your health.
What should I do if I'm not losing 1kg per week after a month?
Weight loss plateaus are normal and don't mean your efforts aren't working. Common reasons include: reduced calorie deficit (as appetite adapts), insufficient physical activity, water retention, or hormonal factors. Consult your GP or a registered dietitian for personalised support, or ask about prescription weight loss medication through NHS weight management services.
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.