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
Free tracker included with every download this week
Protein Calculator for Weight Loss — UK Guide
Adequate protein intake is essential during weight loss to preserve muscle mass and support sustainable results. While a protein calculator can help you determine your daily requirements, many UK adults also benefit from prescription weight management options. If you have a BMI of 30 or above, or 27 or above with weight-related health conditions, you may be eligible for licensed weight loss medication. This guide explains protein's role in weight management and the NHS and private prescription options now available across the UK. Use our free BMI calculator to check your personal BMI and see whether prescription support might be appropriate for you.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 — Mounjaro, Wegovy, and Saxenda
Three prescription medications are currently licensed in the UK for weight management in adults. Mounjaro (tirzepatide) is a once-weekly injection that works as a dual GIP and GLP-1 receptor agonist — clinical trials showed average weight loss of 15–21% of body weight over 72 weeks, though individual results vary significantly. Wegovy (semaglutide) is also a once-weekly GLP-1 injection; clinical evidence from the STEP trials demonstrated approximately 15% average body weight loss at the maximum dose. Saxenda (liraglutide) is a daily GLP-1 injection offering similar mechanisms to Wegovy.
All three are prescription-only and require a clinical assessment before being prescribed. Eligibility typically includes adults with a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with at least one weight-related health condition such as type 2 diabetes, high blood pressure, or cardiovascular disease. South Asian, Chinese, Black African, and Black Caribbean adults may have access to lower BMI thresholds due to higher health risks at those levels. None of these medications are suitable during pregnancy or for people under 18 years old.
Try our free GLP-1 weight loss calculator to explore potential outcomes at different medication doses, and use our weight converter to compare your weight across kg, stone, and lbs measurements.
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
In the UK, prescription weight loss medication can be accessed through two routes: NHS specialist services or private prescribing. NHS access requires referral to a tier 3 specialist weight management service through your GP. These are evidence-based programmes that combine medication with lifestyle support, but waiting lists vary significantly by region and can extend several months or longer in many areas. Private access is available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber — no NHS referral is necessary, though costs typically range from £130–£320 monthly depending on dose.
Start by speaking with your GP about your weight management goals. They can refer you to NHS specialist services if eligible, or discuss whether private options might suit you. Use the BMI calculator on this page to determine your starting point, and track your progress with our free weight loss tracker once you begin any programme. Your GP can also advise on protein requirements and overall nutrition strategy to complement medication.
- 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 much protein do I need during weight loss?
General guidance suggests 1.2–2.2g of protein per kilogram of body weight daily during weight loss, higher than standard recommendations. This preserves muscle mass and supports satiety. Your GP or a registered dietitian can provide personalised guidance based on your individual health and activity level.
Can prescription weight loss medication work without dietary changes?
No. Mounjaro, Wegovy, and Saxenda are most effective when combined with a reduced-calorie diet and increased physical activity. These medications support appetite regulation, but lifestyle changes are essential for sustainable results. Clinical trials consistently showed this combination approach.
Am I eligible for NHS weight loss medication?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related conditions like type 2 diabetes or high blood pressure. Eligibility varies by region. Speak to your GP about referral to specialist weight management services, or use our BMI calculator to check your current BMI.
What's the difference between Mounjaro and Wegovy for weight loss?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist; Wegovy (semaglutide) is GLP-1 only. Clinical trials suggest Mounjaro may produce slightly greater average weight loss, but individual responses vary. Your prescriber will discuss which is most appropriate for you.
How quickly will I lose weight on prescription medication?
Weight loss typically begins within 2–4 weeks, with most significant loss occurring between weeks 8–16. Safe loss is 0.5–1 kg per week. Clinical trials tracked weight loss over 68–72 weeks. Your GP or prescriber will monitor progress and adjust your dose or approach as needed.
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.