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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Thirty Pound Weight Loss: UK Prescription Medication Options
Losing thirty pounds (approximately 13.6 kg) is a significant health goal, and for eligible UK adults, prescription weight management medication may help support this journey. The UK now has several licensed options including Mounjaro, Wegovy, and Saxenda—all prescription-only medicines available through NHS specialist services or private prescribing. If you're considering weight loss medication as part of your approach to weight management in the UK, understanding your eligibility and available options is the essential first step.
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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 GLP-1 and GIP-agonist medications are currently licensed in the UK for weight management:
- Mounjaro (tirzepatide) — A dual GIP and GLP-1 receptor agonist. Administered as a once-weekly injection. Clinical trials showed participants lost an average of 15–21% of body weight, though individual results vary.
- Wegovy (semaglutide) — A GLP-1 receptor agonist. Also given once weekly by injection. Evidence from clinical trials demonstrated average weight loss of approximately 15% of body weight when combined with lifestyle changes.
- Saxenda (liraglutide) — A daily GLP-1 injection (differs from the once-weekly options). Typically results in slightly lower average weight loss compared to Mounjaro and Wegovy.
All three require a prescription and clinical assessment. Eligibility typically includes adults with a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. To check whether you might be eligible and understand your personal BMI context, use our free BMI calculator to see where you currently fall on the NHS weight classification scale.
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 Weight Loss Medication: NHS vs Private
NHS route: Prescription weight loss medication is available through tier 3 and tier 4 specialist weight management services. You'll need a GP referral, and availability varies significantly across different regions and integrated care boards (ICBs). Waiting times can be substantial in some areas. Your GP can discuss referral eligibility and local options.
Private route: Licensed prescribers in the UK offer weight loss medication through online consultations with GPhC-registered pharmacies. Access is faster and doesn't require an NHS referral, though costs vary by dose and provider (typically £129–£320 per month). A clinical assessment is still required to ensure the medication is suitable for you.
Whichever route you choose, weight loss medication works best alongside a reduced-calorie diet and increased physical activity—not as a replacement. Our GLP-1 weight loss calculator can help you estimate potential outcomes at different doses, and our progress tracker allows you to monitor your weight loss journey 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.
How much weight can I realistically lose with prescription medication?
Individual results vary significantly. Clinical trials showed average weight loss of 15–21% of body weight depending on the medication and dose, but some people lose more and some less. Thirty pounds (13.6 kg) represents approximately 5–10% of body weight for most people, which is a realistic target. Results depend on adherence, lifestyle changes, starting weight, and individual metabolism.
Am I eligible for weight loss medication on the NHS?
You may be eligible if you have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions (such as type 2 diabetes, high blood pressure, or cardiovascular disease). Lower BMI thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Speak to your GP about a referral to your local specialist weight management service to check eligibility.
What's the difference between Mounjaro and Wegovy?
Mounjaro is a dual GIP and GLP-1 receptor agonist given once weekly, typically resulting in slightly higher average weight loss (15–21%) than Wegovy in clinical trials. Wegovy is a GLP-1 agonist alone, also once weekly, with average weight loss around 15%. Mounjaro is newer. Both require clinical assessment. Your prescriber will advise which is more appropriate for you.
How quickly will I lose weight on these medications?
Weight loss typically becomes noticeable after 4–8 weeks. The medications are started at a low dose and increased gradually every 4 weeks to improve tolerability. Most significant weight loss occurs between weeks 8 and 20. Safe, sustainable weight loss is generally 0.5–1 kg per week—thirty pounds over 6–8 months is a realistic timeframe with medication plus lifestyle changes.
Are there side effects I should know about?
Common side effects include nausea, diarrhoea, constipation, and stomach pain—typically mild and improving over time as your body adjusts. More serious side effects are rare but can include pancreatitis (severe stomach pain). Always discuss potential side effects with your prescriber. Regular monitoring helps ensure the medication remains safe and effective for you.
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.