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
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Losing 25 Kg — UK Prescription Weight Management Options
Losing 25 kg is a significant health goal that typically requires both lifestyle changes and, for many UK adults, professional support. Prescription weight management medications are now available on the NHS and privately for eligible adults. These include GLP-1 weight loss injections like Mounjaro and Wegovy, which clinical trials have shown can help achieve substantial weight loss when combined with a reduced-calorie diet and increased physical activity. This guide explains your options, eligibility criteria, and how to access support through both NHS and private routes.
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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 Loss Medications
Three main prescription weight management options are licensed in the UK for adults with a BMI of 30 or above (or 27 or above with weight-related health conditions like type 2 diabetes, high blood pressure, or cardiovascular disease):
- Mounjaro (tirzepatide) — dual GIP and GLP-1 receptor agonist, once-weekly injection. Clinical trials showed participants lost an average of 15–21% of their body weight at maximum dose.
- Wegovy (semaglutide) — GLP-1 receptor agonist, once-weekly injection. Clinical evidence demonstrates approximately 14.9% average weight loss at the maximum 2.4 mg dose.
- Saxenda (liraglutide) — GLP-1 receptor agonist, once-daily injection. Average weight loss of approximately 5–6% of body weight in clinical trials.
All are prescription-only medicines requiring a clinical assessment. Individual results vary significantly. These medications work alongside dietary changes and physical activity, not as replacements for lifestyle modifications. Our GLP-1 weight loss calculator can help you estimate potential outcomes at different doses.
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.
Accessing Prescription Weight Loss Treatment in the UK
In England, Mounjaro and Wegovy are now available through NHS specialist tier 3 weight management services, though access and waiting times vary significantly by region and ICB. Many people experience waiting lists of several months. Alternatively, private online prescribing services offer faster access through UK-licensed prescribers and GPhC-registered pharmacies, typically within days, though you'll pay privately (costs vary from approximately £129–£320 monthly depending on dose).
To explore your options: discuss weight loss support with your GP, who can refer you to local NHS services if appropriate; or use our BMI calculator to confirm your BMI category and eligibility criteria, then explore private options if you prefer faster access. Your GP can advise on which route suits your circumstances.
- 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 long does it typically take to lose 25 kg safely using prescription medication?
At the recommended rate of 0.5–1 kg per week, losing 25 kg would take approximately 6–12 months. However, weight loss medication doesn't assures a fixed timeline — results depend on starting weight, dose, individual metabolism, diet, and exercise. Clinical trials show most weight loss occurs in the first 6–12 months of treatment.
Will I be eligible for Mounjaro or Wegovy on the NHS?
You may be eligible if your BMI is 30 or above, or 27 or above with weight-related health conditions (type 2 diabetes, hypertension, heart disease, sleep apnoea). Lower thresholds apply for South Asian, Black African, or Black Caribbean adults. Your GP or a prescriber will assess your eligibility based on your individual health profile and circumstances.
What's the difference between Mounjaro and Wegovy for weight loss?
Mounjaro (tirzepatide) works on two hormone pathways (GIP and GLP-1), whilst Wegovy (semaglutide) works on one (GLP-1). Clinical trials suggest Mounjaro may produce slightly higher average weight loss (15–21% vs 14.9%), though individual responses vary. Both are once-weekly injections. The choice depends on your health profile and what a prescriber recommends.
Can I use our weight converter and BMI calculator to check if I'm eligible?
Yes. Use our BMI calculator to find your current BMI and see which category you fall into. Our weight converter helps track your progress in both metric (kg) and imperial (stone/lbs) measurements. These tools help you understand your baseline and set realistic targets, but only a qualified prescriber can assess your actual eligibility.
Is weight loss medication available privately if NHS waiting lists are too long?
Yes. Private UK-licensed prescribers can issue prescriptions for Mounjaro, Wegovy, and Saxenda following an online clinical assessment. Dispensed by GPhC-registered pharmacies, typically within days. Costs vary (roughly £129–£320 monthly depending on dose and provider). Private access bypasses NHS waiting lists but requires private payment.
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.