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 Lb Weight Loss: UK Prescription Medication Options
Losing 12 pounds (approximately 5.4 kg) is a realistic starting goal for weight management in the UK. If you're considering prescription support alongside lifestyle changes, several GLP-1 and GIP/GLP-1 weight loss medications are now available through both NHS specialist services and private prescribing. This guide explains your options, eligibility criteria, and how to get started. Our free BMI calculator can help you understand where your current weight sits and what a 12 lb loss would mean for your health metrics.
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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 Available
Three prescription medications are currently licensed for weight management 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 receptor agonist.
- Mounjaro: Once-weekly injection, doses 2.5–15 mg. Clinical trials showed average weight loss of 15–21% of body weight. Eligible adults have a BMI of 30+ or 27+ with weight-related health conditions.
- Wegovy: Once-weekly injection, doses 0.25–2.4 mg. Clinical trials showed average weight loss of approximately 15% of body weight alongside diet and exercise changes.
- Saxenda: Daily injection, doses 0.6–3 mg. Established option with proven efficacy for weight management in eligible patients.
Individual results vary significantly. These medications work best when combined with reduced-calorie eating and increased physical activity. Our GLP-1 weight loss calculator can help you estimate potential results at different doses based on clinical trial data.
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 access: Prescription weight loss medications are available through NHS specialist tier 3/4 weight management services. Your GP can refer you for assessment, though waiting times vary significantly by region. Some areas have delays of several months to over a year depending on service capacity and demand.
Private access: Available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber. No NHS referral needed. Costs typically range from £129–£320+ per month depending on the medication and dose you're prescribed. Speak with your GP first to discuss your eligibility and which option suits your situation best.
- 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.
Am I eligible for prescription weight loss medication to lose 12 lbs?
Adults with a BMI of 30 kg/m² or above are generally eligible. If your BMI is 27–29.9, you may be eligible if you have a weight-related health condition such as type 2 diabetes, high blood pressure, or cardiovascular disease. Use our free BMI calculator to check your BMI and discuss eligibility with your GP or a prescriber.
How much weight can I expect to lose with Mounjaro or Wegovy?
Clinical trials showed average weight loss of 15–21% of body weight with Mounjaro and approximately 15% with Wegovy, achieved over several months alongside diet and exercise. For a 12 lb goal, results depend on your starting weight and individual factors. Results always vary between individuals.
Will the NHS prescribe weight loss medication?
Yes, NHS specialist weight management services can prescribe these medications. Access is through referral from your GP to tier 3/4 services. Availability and waiting times vary significantly by region. Contact your local Integrated Care Board to check services in your area.
What's the difference between Mounjaro and Wegovy?
Mounjaro uses a dual GIP and GLP-1 mechanism, while Wegovy uses GLP-1 only. Mounjaro is injected weekly with higher doses (2.5–15 mg); Wegovy is also weekly (0.25–2.4 mg). Both are prescription-only. Your prescriber will assess which is more appropriate for you.
Can I get weight loss injections privately without NHS referral?
Yes. Private online prescribing services offer Mounjaro and Wegovy following a clinical assessment. You'll need to complete a health questionnaire reviewed by a UK-licensed prescriber. If approved, a prescription is issued to a pharmacy. Costs are typically £129–£320+ per month depending on dose and provider.
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.