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
Four Week Weight Loss — What's Realistic?
Losing weight in four weeks is possible, but realistic expectations matter. The NHS recommends losing 0.5 to 1 kg (1 to 2 lbs) per week for sustainable, healthy results — meaning a realistic four-week target is 2 to 4 kg. gradual weight management is often temporary and may not lead to lasting change. This guide explains what evidence shows about four-week weight loss, safe methods, and when to seek professional support. Our free BMI calculator and progress tracker can help you monitor your journey step by step.
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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.
Four Week Weight Loss Targets and Safe Rates
Safe weight loss over four weeks: Following NHS weight management guidance, a realistic target is 2 to 4 kg (4.4 to 8.8 lbs) at a sustainable rate of 0.5 to 1 kg per week. This assumes consistent dietary and lifestyle changes throughout the month.
Why not faster? Losing weight too quickly (more than 1.5 kg per week without medical supervision) increases risk of muscle loss, nutrient deficiencies, gallstones, and muscle loss. Very gradual weight management is also typically not sustainable — most people regain the weight within months.
- 0.5 kg/week = approximately 2 kg over four weeks
- 1 kg/week = approximately 4 kg over four weeks
- Anything faster requires medical oversight
Individual results vary based on starting weight, age, metabolism, and how consistently you maintain dietary changes. Use our free BMI calculator and weight converter to track your current position and set realistic milestones.
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.
Four Week Weight Loss Methods That Work
The most effective approaches for four-week weight management combine reduced-calorie eating with increased physical activity. A calorie deficit of approximately 500 kcal per day typically results in 0.5 kg per week loss. This requires either eating 500 kcal less, burning 500 kcal more through exercise, or a combination of both.
Proven methods include:
- Structured meal planning with balanced portions
- Reducing ultra-processed foods, sugary drinks, and excess fats
- Increasing protein and fibre to support satiety
- Adding 150+ minutes of moderate physical activity weekly
- Drinking adequate water and managing stress
Prescription weight loss medication (such as GLP-1 injections) may be considered as part of NHS weight management in specific cases, though this typically requires referral to a specialist service. Our GLP-1 weight loss calculator can show you potential results if medication is recommended by your GP.
- 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 four weeks?
Following NHS guidance, a realistic target is 2 to 4 kg (4.4 to 8.8 lbs) at a safe rate of 0.5 to 1 kg per week. This assumes consistent dietary and lifestyle changes. Individual results vary based on starting weight, metabolism, and adherence.
Is gradual weight management in four weeks safe?
Losing more than 1.5 kg per week without medical supervision is not recommended by the NHS. Very gradual weight management increases risk of muscle loss, nutrient deficiencies, gallstones, and is often not sustainable — most people regain the weight quickly.
What's the best way to lose weight in four weeks?
Create a calorie deficit of approximately 500 kcal per day through balanced eating and increased physical activity. Focus on whole foods, adequate protein, plenty of vegetables, and regular exercise — typically 150+ minutes weekly of moderate activity.
Should I consider weight loss medication for a four-week goal?
Prescription weight loss medications like Wegovy (semaglutide) or Mounjaro (tirzepatide) are prescription-only and require clinical assessment. They're designed for longer-term weight management, not short-term four-week results. Discuss options with your GP if you have a BMI of 30 or above with health conditions.
How do I track weight loss progress over four weeks?
Weigh yourself weekly at the same time of day, under the same conditions. Our free progress tracker tool lets you log weekly measurements and see trends. Also track how clothes fit, energy levels, and measurements — the scale doesn't tell the whole story.
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.