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
Before and After Weight Loss with UK Medication
When people search for "before after weight loss," they're often looking to understand realistic outcomes from weight management treatment. In the UK, prescription weight loss medications can support significant health improvements, but results vary greatly between individuals. This guide explains how UK-licensed options like Mounjaro and Wegovy work, who is eligible, and what genuine expectations should be. Weight loss is a journey, not just a visual transformation — the real benefits come from improved health markers and lifestyle changes alongside any medication used.
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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 Weight Loss Medications Explained
Three prescription-only weight management medications are currently licensed in the UK: Mounjaro (tirzepatide), a dual GIP and GLP-1 receptor agonist; Wegovy (semaglutide), a GLP-1 receptor agonist; and Saxenda (liraglutide), also a GLP-1 agonist. Clinical trials show these medications may help adults achieve significant weight loss when combined with a reduced-calorie diet and increased physical activity. In the SURMOUNT-1 trial, Mounjaro users lost an average of 15–21% of body weight over 72 weeks. Wegovy's STEP trials showed average weight loss of approximately 15% of body weight. Individual results vary considerably — some people lose more, others less. All three medications work by reducing appetite and helping you feel fuller after eating smaller meals. Eligibility requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Calculate your current BMI using our free BMI calculator to check your starting point.
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 in the UK
NHS access: NICE has approved these medications for NHS specialist weight management services (tier 3/4), but access varies significantly by region and involves referral from your GP. Waiting lists can be lengthy in many areas. Private access: GPhC-registered online pharmacies offer these medications following a clinical assessment with a UK-licensed prescriber — no NHS referral needed. Costs typically range from £129–£320 monthly depending on dose. Either route requires a clinical assessment to confirm eligibility and suitability. Speak with your GP about whether prescription weight loss medication is right for you, or explore private options if NHS waiting times are long in your area. Track your progress using our free progress tracker, whether you choose NHS or private treatment.
- 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 realistic weight loss can I expect from these medications?
Individual results vary significantly. Clinical trials show average weight loss of 15–21% of body weight over several months, but some people lose more and others less. Weight loss depends on the medication, your starting weight, adherence to diet and exercise, genetics, and how your body responds. Your GP or prescriber can give you personalised expectations based on your health profile.
Are before and after photos a good way to measure success?
While visual changes can be motivating, health improvements matter more than appearance. Weight loss medication success is best measured by improvements in blood pressure, blood sugar control, energy levels, joint pain, and overall wellbeing — not just visible changes. Use our free progress tracker to log weight, measurements, and how you feel over time.
How long do these medications take to show results?
Most people notice changes within the first 4–8 weeks, but significant weight loss typically takes 12–16 weeks or longer. The medications work gradually — doses are increased every 4 weeks, and your body needs time to adjust. Sustainable weight loss is slower than rapid loss, but it's more likely to last long-term.
Can I see weight loss results without medication?
Yes. Lifestyle changes alone — reduced-calorie diet, regular physical activity, better sleep, and stress management — can produce meaningful weight loss, especially initial loss. However, some people find medication helps them stick to these changes by reducing cravings and hunger. Your GP can discuss which approach suits you best.
What happens to weight after stopping these medications?
Weight may gradually return if you stop the medication without maintaining the lifestyle changes that supported the loss. These medications are tools to help you change habits — they work best when combined with sustained diet and exercise changes. Long-term weight management usually requires ongoing commitment to healthy behaviours, whether or not you continue medication.
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.