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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Weight Loss Protein Powder and Prescription Options in the UK
Protein powder is a popular supplement used alongside dietary changes to support weight loss, but if you're looking for more comprehensive weight management in the UK, prescription medication options are also available. For adults eligible under NHS weight management guidelines or through private prescribing, medications like Mounjaro and Wegovy have shown significant results in clinical trials. This guide explains both dietary approaches and the prescription weight loss options available to you, helping you understand what might work best for your individual 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 Loss Options
If you're exploring weight loss approaches, it's worth knowing about prescription medications licensed for weight management in the UK. Three main options are available:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist administered once weekly, with clinical trials showing average weight loss of 15–21% of body weight alongside a reduced-calorie diet
- Wegovy (semaglutide) — a GLP-1 receptor agonist given once weekly, demonstrating average weight loss of around 15% of body weight in clinical trials
- Saxenda (liraglutide) — a daily GLP-1 injection, approved for weight management and typically used alongside lifestyle changes
These are prescription-only medicines requiring clinical assessment. Individual results vary, and they work best when combined with dietary changes and increased physical activity — similar to how protein supplementation works alongside other lifestyle modifications. Our GLP-1 weight loss calculator can help you explore potential weight loss outcomes at different doses.
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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 and Private Routes in the UK
In the UK, you can access prescription weight loss medication through two routes. NHS access is available through specialist tier 3/4 weight management services, though waiting times vary significantly by region and availability can be limited. Private access is available through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber, and this route doesn't require an NHS referral.
To find out if you're eligible, use our free BMI calculator to check your starting point. Adults with a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes or high blood pressure, may be eligible. Your GP can advise on NHS options, or you can explore private prescribing pathways — either way, a proper clinical assessment ensures any medication is suitable for your individual health profile.
- 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 does protein powder help with weight loss?
Protein powder increases satiety (feeling full), preserves lean muscle mass during weight loss, and has a higher thermic effect than fats or carbohydrates, meaning your body uses more energy digesting it. It's typically mixed into shakes, smoothies, or foods to boost protein intake alongside a reduced-calorie diet.
What's the difference between Mounjaro and Wegovy for weight loss?
Both are prescription injections given once weekly, but Mounjaro is a dual GIP and GLP-1 agonist (may have a slightly different mechanism), while Wegovy is a GLP-1 agonist only. Clinical trial data suggests comparable weight loss outcomes (15–21% for Mounjaro, around 15% for Wegovy), but individual results vary. Your prescriber will assess which is more suitable.
Can I use protein powder AND prescription weight loss medication together?
Yes, in fact this combination may be beneficial. Protein powder supports muscle preservation and satiety, while prescription medications like Mounjaro or Wegovy work on appetite hormones. Always inform your prescriber about any supplements you're using, and discuss with them how to combine approaches safely.
Am I eligible for prescription weight loss medication in the UK?
Generally, you may be eligible if you have a BMI of 30 or above, or 27 or above with weight-related health conditions like diabetes, high blood pressure, or sleep apnoea. Use our free BMI calculator to check your starting point, then speak to your GP about NHS options or explore private prescribing routes.
How quickly will I lose weight with prescription medication?
Clinical trials show average weight loss of 15–21% of body weight over several months, but individual results vary significantly. Most people experience gradual loss starting from around week 4–8. Prescription medications work best alongside a reduced-calorie diet and physical activity — they're a tool to support lifestyle changes, not a replacement for them.
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.