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 Injections in the UK: What You Need to Know
Weight loss injections are prescription-only medications that may help adults manage excess weight when combined with lifestyle changes. In the UK, several GLP-1 and dual-action medications are licensed for weight management, with access available through both NHS specialist services and private prescribing. These injections work by helping regulate appetite and support feeling fuller after meals. Understanding how they work, who qualifies, and where to access them is essential for anyone considering this weight management approach.
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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.
How Weight Loss Injections Work in the UK
Weight loss injections licensed in the UK contain either GLP-1 receptor agonists (like semaglutide in Wegovy) or dual GIP/GLP-1 agonists (like tirzepatide in Mounjaro). These medications mimic natural hormones your gut produces after eating, which signal to your brain that you're full. They may help reduce appetite and food cravings, slow how quickly food leaves your stomach, and support better appetite control overall.
In clinical trials, these injections have helped adults lose an average of 15–21% of their body weight over 12–18 months when used alongside a reduced-calorie diet and increased physical activity. Individual results vary significantly depending on dose, adherence, and lifestyle factors. Use our free GLP-1 weight loss calculator above to see estimated weight loss projections at different doses based on your starting weight.
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.
UK Eligibility and Access Routes
To access weight loss injections in the UK, you typically need a BMI of 30 or above, or 27 or above if you have weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Lower BMI thresholds (27.5+) may apply if you're from South Asian, Chinese, Black African, or Caribbean backgrounds due to higher health risks at lower weights.
NHS access: Referral to a tier 3 specialist weight management service, though waiting lists vary significantly by region. Private access: Online consultation with a UK-licensed prescriber, available without NHS referral. All routes require a clinical assessment to ensure the medication is suitable for you. Check your BMI using our free BMI calculator to understand your starting point.
- 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.
Are weight loss injections available on the NHS in the UK?
Yes, GLP-1 medications are approved for use within NHS specialist weight management services (tier 3). Access varies significantly by region and waiting lists can be lengthy. Your GP can refer you to your local specialist service, though availability depends on your integrated care board.
What's the difference between Wegovy and Mounjaro?
Wegovy (semaglutide) is a GLP-1 agonist with a single mechanism of action. Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist. Both are once-weekly injections, but Mounjaro may produce slightly larger average weight loss in clinical trials. Individual results vary, and your prescriber will recommend the most suitable option.
How much weight can you lose with weight loss injections in the UK?
Clinical trials show average weight loss of 15–21% of body weight over 12–18 months. However, individual results vary considerably based on the dose used, how consistently you take the medication, and lifestyle changes. Your results depend on many factors including genetics, adherence, and diet.
Can I get weight loss injections privately in the UK?
Yes. GPhC-registered online pharmacies can prescribe weight loss injections following an online clinical assessment with a UK-licensed prescriber. Costs typically range from £129–£320 per month depending on dose and provider. You don't need an NHS referral for private prescribing.
What happens when you stop taking weight loss injections?
Weight tends to return over time if you stop the medication without maintaining the lifestyle changes (reduced-calorie diet and physical activity). Most people regain some weight after stopping, though not always all of it. Your prescriber can discuss long-term management strategies with you.
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.