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
Weight Loss, Protein & Prescription Medication in the UK
Protein plays an important role in weight management, helping you feel fuller for longer and preserving muscle during weight loss. However, for adults in the UK with excess weight and health concerns, prescription medication may also be recommended by a GP or specialist. This guide covers both dietary approaches and the prescription weight management options now available in the UK, including who is eligible and how to access them through the NHS or privately.
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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 Loss Medications
Three prescription-only medications are currently licensed in the UK for weight management in eligible adults:
- Mounjaro (tirzepatide) — A once-weekly injection that activates two hormone pathways (GIP and GLP-1). In clinical trials, participants lost an average of 15–21% of their body weight over 72 weeks when combined with diet and exercise changes.
- Wegovy (semaglutide) — A once-weekly GLP-1 injection. Clinical evidence shows average weight loss of approximately 15% of body weight at the maximum dose, alongside lifestyle modifications.
- Saxenda (liraglutide) — A daily GLP-1 injection offering similar mechanisms to Wegovy but requiring daily rather than weekly injections.
All three are prescription-only and require a clinical assessment to confirm eligibility. Individual results vary significantly.
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 Prescription Options
In the UK, you can access prescription weight loss medication through two routes:
- NHS: Referral to a tier 3 specialist weight management service through your GP. Availability and waiting times vary significantly by region. Your GP can advise whether you meet local eligibility criteria.
- Private: Online consultation with a UK-licensed prescriber, available without NHS referral. A prescription is issued if clinically appropriate and dispensed by a registered pharmacy.
You may also qualify based on your BMI and any weight-related health conditions. Calculate your BMI using our free BMI calculator to get an initial sense of where you fall on the health weight chart. Discuss your options with your GP, who can provide personalised guidance based on 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.
Does protein alone help you lose weight?
Protein is an important part of weight management. It helps you feel fuller for longer, reduces hunger between meals, and helps preserve muscle mass during weight loss. However, sustainable weight loss also requires overall calorie management and physical activity. Protein should be part of a balanced approach, not a standalone solution.
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 (such as type 2 diabetes, high blood pressure, or sleep apnoea) may be eligible. Lower BMI thresholds apply to people of South Asian, Chinese, Black African, or Black Caribbean heritage. A prescriber will assess your individual circumstances.
How much weight can you lose with Mounjaro or Wegovy?
Clinical trials showed average weight loss of around 15–21% of body weight with these medications, but individual results vary significantly. Weight loss depends on your starting weight, adherence to the medication, diet changes, and physical activity. Some people lose more, some less. Results are not assured.
Can I get weight loss injections on the NHS?
Yes, weight loss injections (Mounjaro, Wegovy, Saxenda) are available through NHS specialist weight management services. However, access varies by region and waiting times can be lengthy. Ask your GP about referral to your local tier 3 service. Private access is also available through online prescribing if you prefer to explore that route first.
What's the difference between GLP-1 and GIP/GLP-1 medications?
GLP-1 medications (like Wegovy) activate one hormone pathway. GIP/GLP-1 medications like Mounjaro activate two pathways. The dual mechanism in Mounjaro may result in slightly greater average weight loss in trials, but both are effective. Your prescriber will advise which is most suitable for your circumstances.
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.