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
Weight Loss Results — What's Realistic?
Weight loss results vary significantly between individuals, depending on your starting point, lifestyle changes, and whether you're using medication. The NHS recommends losing weight at a rate of 0.5 to 1 kg per week for sustainable, long-term results. If you're considering prescription weight management options or lifestyle-based approaches, understanding what realistic weight loss results look like is essential for setting achievable goals. Our free BMI calculator and weight loss calculator above can help you assess your current position and explore potential outcomes based on evidence from clinical trials and real-world data.
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.
Expected Weight Loss from Lifestyle Changes and Medication
Lifestyle-based weight loss (diet and exercise alone) typically results in 3–5 kg loss over 6 months, though this varies. A calorie deficit of approximately 500 kcal per day supports losing around 0.5 kg weekly.
GLP-1 weight loss injections (Wegovy/semaglutide) have shown more significant results in clinical trials. The STEP-1 trial found participants lost an average of 14.9% of their body weight over 68 weeks using semaglutide 2.4 mg alongside reduced-calorie diet and increased physical activity. Mounjaro (tirzepatide), a dual GIP/GLP-1 injection, showed average weight loss of approximately 15–21% of body weight in SURMOUNT trials.
Both medications are prescription-only and require clinical assessment. Individual results vary considerably — some people lose more, others less. Weight loss medication works best when combined with lifestyle changes, not as a replacement for them.
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.
Factors Affecting Your Personal Weight Loss Results
Your weight loss results depend on multiple factors: your starting weight, age, genetics, adherence to diet changes, physical activity level, metabolism, and underlying health conditions such as thyroid disease or polycystic ovary syndrome (PCOS). Medications like antipsychotics or steroids can also slow weight loss. Some people naturally lose weight more quickly than others, even following identical programmes.
The NHS weight loss programme emphasises that even a 5–10% reduction in body weight can deliver meaningful health benefits, including improved blood pressure, better blood sugar control, and reduced joint pain. Set realistic goals: aim for 0.5–1 kg weekly loss rather than expecting dramatic results overnight. Track your progress using our free progress tracker to stay motivated and identify what works for you.
- 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 you lose with Wegovy or Mounjaro injections?
Clinical trials show Wegovy (semaglutide) supports average weight loss of around 15% of body weight, while Mounjaro (tirzepatide) shows average loss of 15–21%. However, individual results vary significantly. These results were achieved alongside reduced-calorie diet and increased physical activity. Both are prescription-only medications requiring clinical assessment.
What is the NHS recommended rate of weight loss?
The NHS recommends losing 0.5 to 1 kg per week for sustainable, healthy weight loss. This typically requires a calorie deficit of around 500 kcal daily. Faster weight loss is possible but may increase muscle loss and is not recommended without medical supervision.
Can you lose weight through diet and exercise alone?
Yes. Most people can lose 3–5 kg over 6 months through calorie deficit and increased activity. Results depend on your starting point, adherence, and individual metabolism. Calculate your BMI and healthy weight range using our free BMI calculator to set realistic targets aligned with NHS guidance.
How quickly do weight loss results appear?
Initial weight loss often appears within 2–4 weeks as water weight reduces. Sustainable fat loss typically becomes noticeable after 4–6 weeks of consistent calorie deficit. With GLP-1 medication, weight management results develop gradually over weeks to months alongside lifestyle changes.
What counts as meaningful weight loss?
The NHS confirms that losing just 5–10% of your body weight delivers measurable health benefits: improved blood pressure, better blood sugar control, reduced sleep apnoea severity, and lower joint pain. You don't need to reach a specific number — even modest, sustainable loss improves health outcomes significantly.
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.