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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12 Pound Weight Loss: Prescription Medication Options in the UK
Losing 12 pounds (approximately 5.4 kg) is a realistic and sustainable weight loss goal that can deliver meaningful health benefits. In the UK, prescription weight management medications are now available for eligible adults through both NHS specialist services and private prescribing routes. These medications, known as GLP-1 receptor agonists, work by helping regulate appetite and support feeling fuller after meals. Whether you're starting your weight loss journey or looking to progress further, understanding your medication options is an important first step. This guide covers the prescription weight management options available in the UK, who is eligible, and how to explore treatment with your GP.
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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 medications are currently licensed in the UK for weight management:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist, injected once weekly. In clinical trials, participants lost an average of 15–21% of their body weight; individual results vary significantly.
- Wegovy (semaglutide) — a GLP-1 receptor agonist, injected once weekly. Clinical trial data showed an average weight loss of around 15% of body weight over 68 weeks.
- Saxenda (liraglutide) — a GLP-1 receptor agonist, injected daily. Typically produces more modest weight loss than weekly injections but remains an effective option for some patients.
All three are prescription-only and require a clinical assessment before being prescribed. Losing 12 pounds represents approximately 1–2 weeks of average weight loss on these medications, though individual timelines vary based on starting weight and dose.
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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, you can access prescription weight loss medication through two routes: NHS specialist tier 3 weight management services or private online prescribing from GPhC-registered pharmacies. NHS access typically requires a GP referral and assessment by a specialist weight management team; availability varies significantly by region and waiting lists can be lengthy. Private access is available through online consultations with UK-licensed prescribers without needing an NHS referral.
To find out if you're eligible, calculate your BMI using our free BMI calculator — you'll likely qualify if your BMI is 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes or high blood pressure. Start by speaking with your GP about weight loss medication options, or contact a private prescribing service for an online assessment. Track your progress using our free progress tracker once you begin 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.
How much weight can I expect to lose on prescription weight loss medication?
Results vary significantly between individuals and depend on your starting weight, the medication used, and dose. Clinical trials show average weight loss of 15–21% of body weight, but some people lose more or less. Your GP or prescriber can discuss realistic expectations based on your individual health profile. Losing 12 pounds is a reasonable milestone within the first few weeks of treatment for many people.
Am I eligible for prescription weight loss medication on the NHS?
You may be eligible if you have a BMI of 30 or above, or 25–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. For adults of South Asian, Chinese, Black African, or Caribbean heritage, lower BMI thresholds apply. Your GP can assess your eligibility and refer you to a specialist weight management service if appropriate.
How long does it take to lose 12 pounds with GLP-1 medication?
This depends on your starting weight and the dose you're taking. On average, people lose approximately 0.5–1 kg per week with weight loss medication, meaning 12 pounds (5.4 kg) could take 5–10 weeks. However, weight loss is not linear — some weeks you'll lose more, some weeks less. Consistency with diet and exercise matters significantly.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) works on two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) works on one (GLP-1 alone). Clinical trials suggest Mounjaro may produce slightly greater average weight loss, but both are effective. Both are once-weekly injections. Your prescriber will recommend the best option based on your individual health needs and circumstances.
Can I get prescription weight loss medication without seeing my GP?
Yes — private prescribing services in the UK allow you to access prescription weight loss medication through online consultations without a GP referral. However, it's still advisable to inform your GP if you're taking prescription medication. Private treatment typically involves costs of £130–£320 per month depending on the medication and dose, whereas NHS access is free but may involve longer waiting times.
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.