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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What Are Weight Loss Injections Called in the UK?
Weight loss injections available in the UK go by several brand names, with the most commonly prescribed being Wegovy (semaglutide) and Mounjaro (tirzepatide). These are prescription-only medications that may help reduce appetite and support weight management when used alongside a reduced-calorie diet and increased physical activity. Individual results vary, and they're only suitable for certain people. This guide explains the main names you'll encounter, how they work, and what you need to know before considering treatment in the UK.
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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.
The Main Weight Loss Injections Available in the UK
Three prescription-only weight loss injections are currently licensed in the UK for weight management:
- Wegovy (semaglutide) — a once-weekly GLP-1 receptor agonist injection manufactured by Novo Nordisk. In clinical trials, it helped participants lose an average of around 15% of body weight over 68 weeks.
- Mounjaro (tirzepatide) — a once-weekly dual GIP and GLP-1 receptor agonist injection made by Eli Lilly. SURMOUNT clinical trial data showed average weight loss of 15–21% depending on dose.
- Saxenda (liraglutide) — a daily GLP-1 injection also by Novo Nordisk, though less commonly prescribed than Wegovy for new weight loss cases.
All three require a prescription from a UK-licensed prescriber and a clinical assessment to confirm eligibility. They work by affecting appetite hormones and how your body processes food.
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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.
How to Access Weight Loss Injections in the UK
In the UK, you can access weight loss injections through two main routes:
- NHS specialist services: Referral to a tier 3 or 4 weight management service through your GP. Availability varies significantly by region, and waiting lists can be lengthy.
- Private prescribing: Online consultation with a UK-licensed prescriber, assessment of eligibility, and dispensing through a GPhC-registered pharmacy. This typically takes days rather than months.
Regardless of route, you'll need a BMI of 30 or above (or 27+ with weight-related health conditions like type 2 diabetes or high blood pressure) to be eligible. Use our free BMI calculator to check your starting point, and our GLP-1 weight loss calculator to estimate potential outcomes at different doses.
- 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 Ozempic the same as Wegovy?
Both contain semaglutide, but Ozempic is licensed for type 2 diabetes (doses up to 2mg), while Wegovy is the weight management version (up to 2.4mg). Wegovy is the licensed option for weight loss in the UK; using Ozempic for weight loss is off-label and not recommended.
Which weight loss injection is most effective?
Clinical trials show both Mounjaro and Wegovy support meaningful weight loss. Mounjaro showed slightly higher average weight loss in trials (15–21%) compared to Wegovy (around 15%), but individual results vary significantly. Your prescriber will recommend the most suitable option based on your health profile.
Can I get weight loss injections on the NHS?
Yes, but availability is limited. NICE has approved tirzepatide (Mounjaro) for specialist NHS weight management services, though access varies by region. Most people currently access these through private prescribing services rather than waiting for NHS referral.
What's the difference between GLP-1 and GIP/GLP-1 injections?
GLP-1 injections (like Wegovy) work on one appetite hormone pathway. GIP/GLP-1 injections (like Mounjaro) activate two pathways simultaneously, which may explain slightly higher average weight loss in trials. Both require prescription and clinical assessment.
How do I know if weight loss injections are right for me?
A UK-licensed prescriber will assess your BMI, medical history, current medications, and weight-related health conditions. You'll need a BMI of 30+ (or 27+ with qualifying conditions). Use our weight converter and BMI calculator to understand your current weight status, then consult a prescriber for personalised guidance.
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.