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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Best Options for Weight Loss and Muscle Health — UK Prescription Guide
While supplements can support fitness goals, prescription weight loss medication may be more effective for eligible adults in the UK. If you're looking to lose weight and build muscle, prescription options like Mounjaro and Wegovy offer evidence-based alternatives backed by clinical trials. These medications work alongside diet and exercise, not instead of them. Understanding what's available through the NHS and private prescribing can help you make informed decisions about your weight management journey.
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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 Management Options
Three prescription medications are currently licensed in the UK for weight management:
- Mounjaro (tirzepatide) — A dual GIP and GLP-1 receptor agonist. In clinical trials, participants lost an average of 15–21% of their body weight alongside a reduced-calorie diet and increased physical activity. Doses range from 2.5 mg to 15 mg once weekly.
- Wegovy (semaglutide) — A GLP-1 receptor agonist. Clinical trials showed average weight loss of approximately 15% of body weight. Doses escalate from 0.25 mg to a maximum of 2.4 mg once weekly.
- Saxenda (liraglutide) — A once-daily GLP-1 injection. Approved for weight management but less commonly prescribed than Mounjaro and Wegovy in recent years.
All three require a prescription following a clinical assessment. Individual results vary, and these medications work best when combined with lifestyle changes including reduced calorie intake and increased physical activity.
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 Access vs Private Prescribing — What You Need to Know
NHS access to prescription weight loss medication is through specialist tier 3 or tier 4 weight management services, typically requiring a GP referral. Availability varies significantly by region, and waiting times can be lengthy. You'll need a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea.
Private prescribing is available through GPhC-registered online clinics without NHS referral. A licensed UK prescriber will assess your suitability following an online consultation. Costs typically range from £129 to £320 per month depending on the medication and dose. Try our free GLP-1 weight loss calculator to explore potential outcomes at different dose levels, and use our BMI calculator to check whether you might meet eligibility criteria.
- 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.
What's the difference between supplements and prescription weight loss medication?
Supplements are largely unregulated and evidence of effectiveness is mixed. Prescription medications like Mounjaro and Wegovy are rigorously tested in clinical trials and must meet strict safety and efficacy standards set by the MHRA. They work on specific appetite and blood sugar pathways, whereas supplements have variable and often limited evidence for weight loss. Always discuss options with your GP.
Can I take prescription weight loss medication alongside resistance training for muscle growth?
Yes, many people combine prescription weight loss medication with exercise. However, gradual weight management without adequate protein intake can lead to muscle loss. A balanced approach with sufficient protein, resistance training, and medical supervision is important. Your prescriber can advise on managing protein intake while on medication.
Who is eligible for NHS-funded weight loss medication in the UK?
NHS prescribing is typically available to adults with a BMI of 30 or above, or 27 or above with weight-related health conditions. South Asian, Chinese, Black African, or Black Caribbean adults may be eligible at lower BMI thresholds. Access requires specialist referral and varies by region. Speak to your GP about local services and waiting times.
How long do you need to take Mounjaro or Wegovy?
Treatment duration varies. Some people continue long-term as weight loss and weight regain can occur if stopped. Others use it short-term to kickstart lifestyle change. Your prescriber will discuss the best approach for your individual situation and goals. Regular reviews help determine ongoing suitability.
What is the best approach — supplements, diet alone, or prescription medication?
The best approach depends on your individual health, BMI, and weight-related conditions. For eligible adults, prescription medication combined with a reduced-calorie diet and exercise is evidence-based. Use our free BMI calculator to assess where you stand on the NHS weight chart, then discuss all options including supplements, lifestyle change, and prescription medication with your GP.
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.