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
Eight Week Weight Loss — What's Realistic in the UK?
Eight weeks is enough time to see meaningful weight loss results if you combine dietary changes with increased physical activity. In the UK, the NHS recommends losing weight at a rate of 0.5 to 1 kg per week for sustainable, healthy outcomes. Over eight weeks, this translates to between 4 and 8 kg (roughly 9 to 18 lbs or just over half a stone to just over a stone) of realistic weight loss. The speed of your results depends on your starting weight, metabolism, age, and how consistently you follow your chosen approach. Everyone's body responds differently, so individual results vary significantly.
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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.
Realistic Weight Loss Over Eight Weeks
Safe, sustainable weight loss typically ranges from 4–8 kg over eight weeks if you maintain a calorie deficit of around 500 kcal per day. This deficit is most effectively achieved by combining reduced-calorie eating with regular physical activity—aiming for at least 150 minutes of moderate-intensity activity per week, as recommended by the NHS.
Your personal eight-week outcome depends on several factors: starting weight (people with higher starting weights often lose faster initially), age, gender, muscle mass, and how strictly you stick to your plan. Weight loss is not linear—you may lose more in weeks 1–2 (partly water weight), then settle into steady fat loss of 0.5–1 kg per week.
- Weeks 1–2: 1–2 kg loss (includes water weight)
- Weeks 3–8: 0.5–1 kg per week (fat loss)
- Total realistic range: 4–8 kg over eight weeks
Use our free BMI calculator to track how your BMI changes across your eight-week journey, and our weight converter to monitor progress in your preferred units—stone, kg, or lbs.
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.
Methods for Eight Week Weight Loss Success
Dietary approach: A reduced-calorie diet (1200–1800 kcal daily depending on your starting weight) combined with regular exercise produces the most consistent results. The Mediterranean diet and low-carbohydrate approaches both have strong evidence for weight management in the UK.
Prescription medication: For eligible adults, prescription weight loss medication such as GLP-1 injections (including Wegovy, semaglutide) may support faster results alongside diet and exercise. In clinical trials, semaglutide helped participants achieve average weight loss of around 15% over similar timeframes, though individual results vary. Prescription weight loss medication requires a clinical assessment and ongoing GP or specialist monitoring.
Track your progress consistently using our free progress tracker—seeing measurable results each week increases motivation and helps you stay on course for eight 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.
How much weight can I realistically lose in eight weeks?
The NHS recommends losing 0.5–1 kg per week for sustainable results. Over eight weeks, expect 4–8 kg of weight loss, depending on your starting weight, consistency, and metabolism. Initial weeks may show faster loss due to water weight; fat loss typically stabilises at 0.5–1 kg weekly.
Is eight weeks enough time to see visible changes?
Yes. Losing 4–8 kg is usually visible in how clothes fit, energy levels, and how you feel physically. Changes in BMI are measurable within this timeframe. Use the BMI calculator on this page to track your progress from week one to week eight.
Can I use weight loss injections like Wegovy over eight weeks?
Wegovy (semaglutide) is a prescription-only GLP-1 injection. In clinical trials (STEP studies), participants using semaglutide achieved significant weight loss over similar periods. However, dosing typically starts low and increases over weeks, so full benefit may take longer than eight weeks. Your GP or prescriber assesses eligibility and timing.
What's the safest way to lose weight in eight weeks?
Combine a moderate calorie deficit (500 kcal daily) with regular physical activity and consistent dietary habits. Avoid very low-calorie diets unless supervised by your GP. Weight loss medication is available for eligible adults through NHS specialist services or private prescription—always requires clinical assessment.
How do I stay motivated for eight weeks?
Set weekly targets, track progress using our free progress tracker, weigh yourself weekly (same day/time), and take measurements as well as monitoring BMI. Share your goal with friends or family, join a support group, and celebrate non-scale wins like improved energy or better sleep. Eight weeks is a realistic timeframe where you'll see genuine results.
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.