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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30 Kilo Weight Loss: UK Prescription Medication Options
Losing 30 kilograms is a significant health goal, and prescription weight management medication may help eligible adults in the UK achieve this alongside diet and exercise. If you have a BMI of 30 or above, or 27 or above with weight-related health conditions, you may qualify for prescription weight loss treatment. Three licensed medications are available in the UK: Mounjaro, Wegovy, and Saxenda. Understanding your options, eligibility, and how to access these medications through the NHS or privately is the first step. Use our free BMI calculator above to check your current status and explore what weight management options might be suitable for you.
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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 prescription-only medications are currently licensed in the UK for weight management and may support losing significant amounts of weight when combined with dietary changes and increased physical activity.
Mounjaro (tirzepatide) is a once-weekly injection that works as a dual GIP and GLP-1 receptor agonist. Clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks — which could mean a loss of approximately 15–21kg for someone weighing 100kg. Starting dose is 2.5mg, escalating to a maximum of 15mg per week.
Wegovy (semaglutide) is also a once-weekly injection, working as a GLP-1 receptor agonist. Clinical trial data showed an average weight loss of around 15% of body weight at the maximum dose of 2.4mg weekly. Starting dose is 0.25mg.
Saxenda (liraglutide) is a daily injection with similar GLP-1 action. Maximum dose is 3mg per day.
All three are prescription-only medicines requiring a clinical assessment before being prescribed. Individual results vary significantly based on adherence, lifestyle changes, and personal factors.
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 Eligibility
In the UK, eligibility for prescription weight loss medication requires a BMI of 30kg/m² or above, or 27–29.9kg/m² with at least one weight-related health condition such as type 2 diabetes, high blood pressure, or sleep apnoea. Through the NHS, you would be referred to a tier 3 specialist weight management service by your GP — however, waiting lists vary significantly by region and can be lengthy. Through private prescribing, you can access these medications via an online consultation with a UK-licensed prescriber without an NHS referral, though costs typically range from £129–£320 per month depending on dose.
Your GP can discuss which route is most appropriate for you and assess whether prescription treatment is suitable alongside lifestyle changes. Many people combine medication with our free weight loss calculator and progress tracker to monitor results over time.
- 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 lose 30kg with prescription weight loss medication?
Clinical trials show Mounjaro and Wegovy help participants lose 15–21% of their body weight on average. For someone weighing 100kg, this could mean approximately 15–21kg loss. However, individual results vary significantly. Medication works best alongside a reduced-calorie diet and increased physical activity. Your prescriber can give you realistic expectations based on your circumstances.
Am I eligible for prescription weight loss medication on the NHS?
You may be eligible if your BMI is 30 or above, or 27–29.9 with weight-related health conditions like diabetes, high blood pressure, or sleep apnoea. For people of South Asian, Chinese, or Black African heritage, lower BMI thresholds may apply. Your GP can assess your eligibility and refer you to specialist services where available.
How long does it take to lose 30kg with these medications?
Weight loss is gradual and sustainable. Losing 0.5–1kg per week is considered safe and realistic. Reaching a 30kg loss at this rate would take approximately 30–60 weeks (6–14 months). Medication dose escalation happens gradually over 16–20 weeks, so initial results build over time. Consistent diet and exercise are essential.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP+GLP-1 agonist; Wegovy (semaglutide) is a GLP-1 agonist only. Clinical evidence suggests Mounjaro may produce slightly higher average weight loss (up to 21% vs 15%). Both are once-weekly injections. Wegovy has longer clinical trial data for weight management. Your prescriber will advise which is more suitable for you.
How do I start prescription weight loss medication?
Contact your GP to discuss weight management options. They can assess your eligibility and either refer you to NHS tier 3 specialist services or advise on private prescribing routes. Private access involves an online consultation with a UK-licensed prescriber. Either way, a clinical assessment is required before prescription. Use our weight loss calculator to estimate potential outcomes alongside your GP consultation.
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.