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 Intake and Weight Loss — What UK Adults Need to Know
Protein plays a key role in weight loss by helping you feel fuller for longer and preserving muscle mass during calorie reduction. While increasing protein intake and following a reduced-calorie diet form the foundation of sustainable weight management, prescription medications are also available in the UK for eligible adults. This guide explains how protein supports weight loss and when prescription weight loss treatment might be appropriate for you.
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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 Prescription Weight Loss Options for Eligible Adults
If you're struggling with weight management through diet and exercise alone, the UK offers several prescription weight loss medications that work alongside lifestyle changes. These are available through NHS specialist weight loss services or private online prescribing following a clinical assessment.
- Mounjaro (tirzepatide) — A dual GIP and GLP-1 receptor agonist, injected once weekly. Clinical trials showed participants lost an average of 15–21% of their body weight, though individual results vary significantly.
- Wegovy (semaglutide) — A GLP-1 receptor agonist, injected once weekly. Evidence from clinical trials demonstrated average weight loss of approximately 15% of body weight when combined with a reduced-calorie diet and increased physical activity.
- Saxenda (liraglutide) — A GLP-1 receptor agonist injected once daily. Also available on prescription for weight management.
All three are prescription-only medicines requiring assessment by a healthcare professional to establish eligibility and suitability. Try our GLP-1 weight loss calculator to explore potential outcomes at different medication doses.
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 vs Private Access — How to Find Out if You're Eligible
Access to weight loss medication on the NHS is through tier 3 specialist weight management services, typically requiring a GP referral. Waiting lists vary significantly by region, and availability depends on your local integrated care board. Private prescribing offers faster access without NHS referral, following an online consultation with a UK-licensed prescriber.
You are generally eligible if you have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. South Asian, Chinese, Black African, and Black Caribbean adults may be eligible at lower BMI thresholds. Check your BMI using our free BMI calculator, then speak with your GP about whether prescription weight loss treatment is right for you.
- 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.
Does protein help with weight loss?
Yes. Protein increases satiety (fullness), supports muscle preservation during weight loss, and has a higher thermic effect than carbohydrates or fats — meaning your body uses more energy digesting it. Combined with a calorie deficit, adequate protein intake supports sustainable weight loss. Most adults aiming for weight loss should aim for 1.2–2.0g protein per kg of body weight daily.
Can weight loss medication replace diet and protein intake?
No. GLP-1 and GIP/GLP-1 medications like Mounjaro and Wegovy are designed to work alongside a reduced-calorie diet and increased physical activity. They reduce appetite and support lifestyle changes — they do not replace the need for healthy eating, including adequate protein. Your prescriber will emphasise this.
Who is eligible for prescription weight loss medication in the UK?
Adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions, may be eligible. These conditions include type 2 diabetes, high blood pressure, obstructive sleep apnoea, or cardiovascular disease. Eligibility is assessed individually. Speak with your GP to discuss whether you qualify.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Both are once-weekly injections. Mounjaro showed slightly higher average weight loss in clinical trials (15–21% vs approximately 15%), but results vary individually. Your prescriber will discuss which is more suitable for you.
How do I access weight loss medication on the NHS?
Ask your GP for a referral to your local tier 3 specialist weight management service. They will assess your eligibility and may prescribe medications if appropriate. Alternatively, private online prescribing is available through GPhC-registered pharmacies without NHS referral. Costs and waiting times differ between NHS and private routes.
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.