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
Six Week Weight Loss — Realistic Goals and UK Options
Losing weight in six weeks is achievable, but the amount depends on your starting point, lifestyle changes, and whether you use prescription medication. The NHS recommends losing 0.5 to 1 kg per week for sustainable, healthy results — which means six weeks could realistically bring a loss of 3 to 6 kg (approximately 7 to 14 lbs or half to one stone). However, individual results vary significantly based on diet, exercise, metabolism, and genetics. This guide covers realistic timescales, safe weight loss methods, and how prescription weight loss medication fits into the picture for eligible UK adults.
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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.
What's a Safe Weight Loss Rate Over Six Weeks?
The NHS recommends losing no more than 0.5 to 1 kg per week for sustainable weight management without losing muscle mass. Over a six-week period, this translates to 3 to 6 kg total weight loss — a realistic and achievable goal for most adults.
Faster weight loss is possible but carries risks: losing more than 1.5 kg per week can lead to muscle loss, gallstones, nutritional deficiencies, and reduced metabolic rate. Very gradual weight management also tends to be regained quickly because it's often unsustainable.
For weight management in the UK, your GP or a healthcare professional can assess your individual circumstances. Use our free BMI calculator to understand your current starting point and healthy weight range, then set realistic targets based on 0.5 to 1 kg per week loss.
Calorie deficit required: To lose 0.5 kg per week, you need a deficit of approximately 500 kcal per day. To lose 1 kg per week, you need a 1,000 kcal daily deficit — which is substantial and often requires both diet and exercise combined.
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.
Six Week Weight Loss with Prescription Medication
For eligible UK adults, prescription weight loss medications like Wegovy (semaglutide) or Mounjaro (tirzepatide) may support weight loss alongside dietary changes. In clinical trials, these GLP-1 receptor agonist medications helped participants lose an average of 14 to 21% of their body weight over several months — though results over six weeks alone would be more modest as doses are built up gradually.
Prescription weight loss injections work by reducing appetite, helping you feel fuller after smaller meals, and supporting healthier food choices. However, they are prescription-only and require clinical assessment from a GP or licensed prescriber to determine eligibility. Weight management in the UK through NHS specialist services or private prescribing always combines medication with lifestyle changes — diet and exercise remain essential.
Try our free GLP-1 weight loss calculator to explore potential outcomes at different doses over longer timescales.
- 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 a stone in six weeks?
Losing one stone (6.4 kg) in six weeks would require a deficit of approximately 1,500 kcal per day — unsafe without medical supervision. The NHS recommends 0.5 to 1 kg per week maximum, which means six weeks typically brings 3 to 6 kg loss. Faster weight loss increases muscle loss and regain risk. Always consult your GP for personalised guidance.
What's the fastest safe way to lose weight in six weeks?
Combine a moderate calorie deficit (500–750 kcal per day) with regular exercise. A reduced-calorie diet of 1,500 to 1,800 kcal per day plus 150 minutes weekly moderate activity typically supports 0.5 to 1 kg weekly loss. Prescription medication is an option if eligible. Never drop below 1,200 kcal daily without medical supervision.
How much weight loss is realistic with Wegovy in six weeks?
Six weeks is early in Wegovy treatment — doses are increased gradually over the first four to five months. Initial six-week weight loss is typically modest (1 to 3 kg) as your body adjusts. After 12 to 16 weeks at therapeutic doses, average weight loss is around 14% of body weight in clinical trials. Individual results vary significantly.
Will I regain weight after six weeks if I stop dieting?
Yes — weight loss is maintained through sustained lifestyle changes. Returning to previous eating habits typically results in regain. Successful long-term weight management requires permanent changes to diet and exercise. For some people, prescription medication supports these changes, but it works alongside behaviour change, not instead of it.
Is six weeks enough time to see health improvements from weight loss?
Yes. Even modest weight loss (5% of body weight) can improve blood pressure, blood sugar control, and joint pain. Six weeks of consistent 0.5 to 1 kg weekly loss (3 to 6 kg total) can have measurable health benefits. Use our free progress tracker to monitor changes over six weeks and beyond.
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.