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
What's Normal Weekly Weight Loss in the UK?
Normal weekly weight loss in the UK is typically 0.5 to 1 kilogram (1 to 2 pounds) per week, according to NHS guidance. This rate is considered safe and sustainable for most adults and helps preserve muscle mass while reducing body fat. Weight loss varies between individuals based on starting weight, age, metabolism, and whether you're using lifestyle changes alone or combining them with prescription weight management medication. Understanding what's realistic helps you set achievable goals and maintain motivation.
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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.
UK-Licensed Prescription Weight Management Options
For adults struggling to lose weight through diet and exercise alone, prescription weight management medications are available in the UK. Three GLP-1 and GIP receptor agonist medications are licensed for weight loss: Mounjaro (tirzepatide), which is a dual GIP and GLP-1 agonist, and Wegovy (semaglutide) and Saxenda (liraglutide), both GLP-1 agonists.
Clinical trials show that these medications, when combined with a reduced-calorie diet and increased physical activity, support sustainable weight management. Eligibility is typically for adults with a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. All prescription weight loss medications require a clinical assessment by a licensed prescriber and are prescription-only in the UK.
Try our free GLP-1 weight loss calculator to explore potential outcomes at different medication doses alongside lifestyle changes.
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.
NHS vs. Private Access and Getting Started
In the UK, access to prescription weight loss medication is available through two routes. NHS access is through specialist tier 3 weight management services (referral from your GP required), though availability and waiting times vary significantly by region and ICB. Private access is through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber.
The first step is a conversation with your GP about your weight loss goals and whether prescription medication might be suitable. Your GP can assess your eligibility, discuss NHS referral options, and advise on whether medication combined with dietary changes and physical activity is appropriate for you. Use our free BMI calculator to check your BMI category before your appointment—this helps the conversation.
Q1: Is losing 1 kilogram per week too fast? A1: The NHS recommends losing 0.5 to 1 kg per week as a safe, sustainable rate. Faster loss is possible with medical support but increases the risk of muscle loss and nutritional deficiency. Aim for consistent, moderate loss rather than rapid results. Even modest weight loss of 5–10% of body weight brings meaningful health benefits. Q2: How much weight can prescription medication help me lose? A2: Clinical trials show GLP-1 medications support loss of approximately 15–21% of body weight over several months, alongside reduced-calorie diet and exercise. Individual results vary significantly depending on dose, adherence, lifestyle changes, and metabolism. Our weight loss calculator can estimate potential outcomes based on your starting weight and medication dose. Q3: Can I lose weight without medication? A3: Yes. A calorie deficit of around 500 kcal per day typically results in loss of approximately 0.5 kg per week through diet and exercise alone. Many people achieve sustainable weight loss this way. However, if you've tried lifestyle changes and struggle to continue them, prescription medication prescribed by your GP may provide additional support. Q4: Do I need to change my diet if I take weight loss medication? A4: Yes. Prescription weight loss medications work best alongside a reduced-calorie diet and increased physical activity. Medication helps manage appetite and cravings, but without dietary changes and movement, weight loss will be limited. The combination of medication plus lifestyle changes produces the best results. Q5: How do I find out if I'm eligible for NHS weight loss medication? A5: Speak to your GP about your weight and health goals. They can assess your BMI, discuss any weight-related health conditions, and refer you to a specialist weight management service if appropriate. NHS eligibility typically requires BMI of 30 or above, or 27 or above with comorbidities. Availability varies by region and waiting lists may apply.- 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.
What is BMI and how is it calculated?
BMI (Body Mass Index) is calculated by dividing your weight in kilograms by your height in metres squared. It's the standard screening tool used by the NHS to assess whether adults are a healthy weight.
Is BMI accurate for everyone?
BMI is a useful screening tool but doesn't account for muscle mass, bone density, or body fat distribution. Athletes may have a high BMI without excess fat. The NHS recommends using BMI alongside waist circumference for a more complete picture.
What are GLP-1 medications like Mounjaro and Wegovy?
GLP-1 receptor agonists are prescription medications that mimic gut hormones to reduce appetite and help with weight loss. Mounjaro (tirzepatide) and Wegovy (semaglutide) are the two most widely used for weight management in the UK.
Am I eligible for GLP-1 weight loss medication in the UK?
Generally, you need a BMI of 30+ (obese) or 27+ with a weight-related health condition. You must be 18 or over. Use our BMI calculator to check.
What is the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist with up to 22.5% weight loss. Wegovy (semaglutide) is GLP-1-only with up to 15-17% weight loss. Both are weekly injections.
Is this website free to use?
Yes, 100% free. No sign-up required. All tools work instantly in your browser and no personal data is stored on our servers.
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.