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
6 Month Weight Loss: Realistic Expectations in the UK
Losing weight over six months gives your body time to adapt and helps you build sustainable habits. In the UK, the NHS recommends losing weight at a rate of 0.5 to 1 kg per week for safe, long-term results. Over six months, this typically means losing between 12 and 26 kg, depending on your starting point and the approach you take. This guide covers realistic targets, evidence-based methods, and prescription weight loss options available in the UK today.
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.
How Much Weight Can You Lose in 6 Months?
The amount of weight you can lose in six months depends on several factors: your starting weight, the calorie deficit you maintain, your activity level, age, and genetics. A safe, sustainable rate is 0.5–1 kg per week, which means over 26 weeks you could realistically lose 13–26 kg (2 stone to 4 stone 2 lbs). Some people lose more quickly initially, while others progress more gradually.
- Calorie deficit approach: A deficit of 500 kcal per day typically results in 0.5 kg loss per week. A 750 kcal deficit supports 0.75 kg per week.
- With lifestyle changes alone: Most people lose 5–10% of body weight over six months through diet and exercise.
- With prescription weight loss medication: Clinical trials show GLP-1 medications like Wegovy (semaglutide) may help achieve 10–clinically studied weight loss over six months when combined with reduced-calorie diet and increased physical activity.
Use our free BMI calculator above to check your starting point, and our weight loss calculator can help you estimate potential outcomes with different approaches.
Clinically BackedWeight 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.
Safe Weight Management Across Six Months
Sustainable weight loss isn't about rapid results—it's about lasting change. The NHS recommends a gradual approach that protects muscle mass and keeps your metabolism stable. Set a target of losing 10–15% of your body weight over six months rather than aiming for a specific number.
- Track your progress weekly using our free progress tracker—weight fluctuates daily, so weekly averages are more meaningful.
- Combine dietary changes (reduced calories, balanced nutrition) with at least 150 minutes of moderate physical activity per week.
- If you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions, your GP can assess whether prescription weight loss medication might support your goals.
- Aim for sustainable habits you can maintain long-term, not crash diets.
- 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 support gradual weight management safely?
Losing 30 kg in six months (approximately 1.2 kg per week) exceeds the NHS recommended safe rate of 0.5–1 kg per week and risks muscle loss, nutritional deficiency, and metabolic slowdown. A safer target is 12–26 kg over six months. If you have significant weight to lose, your GP can discuss a longer timeframe or prescription support.
Does prescription weight loss medication work in 6 months?
Yes. Clinical trials of Wegovy (semaglutide) show participants lost an average of 14.9% body weight over 68 weeks. Over six months with prescription medication alongside diet and exercise, you may see meaningful weight loss, though individual results vary. Your prescriber will assess whether this is suitable for you.
What's the difference between weight loss with diet alone versus medication?
Diet and exercise alone typically result in 5–clinically studied weight loss over six months. GLP-1 weight loss medications like Wegovy (prescription-only, for eligible adults) combined with lifestyle changes may help achieve 10–15% or more. Medication works by reducing appetite and supporting portion control alongside your dietary efforts.
How do I know if I'm losing weight at a healthy rate?
A healthy rate is 0.5–1 kg per week, or roughly 2–4 kg per month. Weigh yourself weekly at the same time of day on the same scales, then calculate the monthly average—daily weight fluctuates due to hydration and food intake. Use our progress tracker to log weekly weights and spot trends.
Should I see my GP before starting a 6-month weight loss plan?
Yes. Your GP can check your overall health, rule out underlying conditions affecting weight, and discuss whether prescription weight loss medication might support you. For weight loss management in the UK, your GP can refer you to NHS tier 2 or tier 3 weight management services depending on your BMI and health needs.
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.