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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Protein Powder for Weight Loss — And When Prescription Medication Helps
Protein powder can be a useful addition to a weight management plan, but it works best alongside a reduced-calorie diet and physical activity. For many UK adults looking to lose weight, prescription weight management medication may be available. If you have a BMI of 30 or above, or 27 or above with weight-related health conditions, you might be eligible for prescription treatments such as Mounjaro or Wegovy. This guide explains both dietary approaches and the prescription options available in the UK, so you can have an informed conversation with your GP about the best approach for your situation.
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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
For adults in the UK with a BMI of 30 or above (or 27–29.9 with weight-related conditions), several prescription weight loss medications are available through the NHS or private prescribers. Mounjaro (tirzepatide) is a once-weekly GIP and GLP-1 receptor agonist injection that clinical trials showed helped participants lose an average of 15–21% of their body weight. Wegovy (semaglutide) is another once-weekly GLP-1 injection licensed for weight management in the UK, with trial data showing approximately 15% average body weight loss. Saxenda (liraglutide) is a daily GLP-1 injection also available in the UK.
All three are prescription-only medicines and require a clinical assessment before being prescribed. They work best when combined with dietary changes and increased physical activity — similar to how protein powder is most effective as part of a structured weight loss plan, not in isolation. Individual results vary considerably, and a prescriber will assess what's suitable for your specific health circumstances.
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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 Access vs Private Prescription — How to Find Out What's Available
NHS access: Prescription weight loss treatment is available through specialist tier 3 and 4 weight management services, but referral is typically required from your GP. Access varies significantly by region and waiting lists can be lengthy. Ask your GP about specialist weight management services in your local integrated care system.
Private access: Prescription weight loss medication is available through UK-registered online prescribers following a clinical assessment. This option does not require an NHS referral.
Whether you choose protein powder alone, combine it with lifestyle changes, or explore prescription medication options, use our free BMI calculator to understand your starting point. If you're considering GLP-1 medication, our GLP-1 weight loss calculator can help estimate potential results at different doses. Our progress tracker is also valuable for logging weight changes over time, whether you're using dietary supplements or prescription support.
- 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.
Is protein powder enough for weight loss on its own?
Protein powder can support weight loss by helping you feel fuller and maintain muscle during a calorie deficit, but it's most effective as part of a structured plan that includes a reduced-calorie diet and physical activity. For many people, protein powder alone is not sufficient, which is why prescription weight management medication may be helpful for eligible UK adults.
How do I know if I'm eligible for prescription weight loss medication in the UK?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or cardiovascular disease. Lower BMI thresholds apply if you are of South Asian, Chinese, Black African, or Black Caribbean heritage. Your GP can assess your individual eligibility.
What's the difference between Mounjaro and Wegovy for weight loss in the UK?
Both are once-weekly prescription injections licensed for weight management in the UK. Mounjaro (tirzepatide) works on two hormone pathways (GIP and GLP-1) and showed approximately 15–21% average weight loss in trials. Wegovy (semaglutide) works on GLP-1 alone and showed approximately 15% average weight loss. Individual results vary, and your prescriber will advise which is most suitable.
Can I get Mounjaro or Wegovy on the NHS?
Yes, these medications are available through NHS specialist weight management services, but access requires referral from your GP and availability varies by region. Private prescription is also available through UK-registered online prescribers. Ask your GP about options in your area.
Should I use protein powder if I'm taking prescription weight loss medication?
Protein powder can complement prescription medication well, as it helps maintain muscle mass during weight loss and supports satiety. However, any combination of supplements and medication should be discussed with your prescriber to ensure they work together safely and effectively for your situation.
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.