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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Weight Loss Injections on the NHS — Are They Free?
Weight loss injections like semaglutide (Wegovy) and tirzepatide (Mounjaro) are available on the NHS, but access is limited and varies significantly by region. Free access depends on meeting strict eligibility criteria and being referred to a specialist tier 3 weight management service. Many people cannot access these medications through the NHS due to waiting lists and regional availability, making private prescriptions a common alternative. This guide explains how NHS weight loss injections work, who qualifies, and what to expect.
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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.
How to Access Weight Loss Injections on the NHS
To access prescription weight loss medication on the NHS, you must first be referred to a specialist tier 3 weight management service by your GP. Eligibility criteria include:
- BMI of 30 kg/m² or above, or
- BMI of 27–29.9 kg/m² with at least one weight-related health condition (type 2 diabetes, high blood pressure, heart disease, sleep apnoea, or abnormal blood fats)
- For South Asian, Chinese, Black African, or Black Caribbean adults, lower BMI thresholds may apply (from BMI 27.5)
However, NHS access is heavily constrained. Many regions have long waiting lists (sometimes 18+ months), and availability depends on your local Integrated Care Board (ICB). Even when referred, NHS specialists typically prescribe these injections alongside mandatory lifestyle changes including reduced-calorie diet and increased physical activity. Many people find private prescriptions more accessible, available without NHS referral through licensed UK prescribers following an online clinical assessment.
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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 Weight Loss Injections Work and What to Expect
Weight loss injections contain GLP-1 receptor agonists (such as semaglutide in Wegovy) or dual GIP and GLP-1 agonists (such as tirzepatide in Mounjaro). These medications work by mimicking natural hormones that regulate appetite and blood sugar. They help you feel fuller after smaller meals, reduce food cravings, and slow how quickly food leaves your stomach.
In clinical trials, Wegovy helped patients lose an average of approximately 15% of their body weight over 68 weeks alongside diet and exercise. Results vary significantly between individuals. Common side effects include nausea, diarrhoea, and constipation, which often improve over time. Use our free GLP-1 weight loss calculator to estimate potential weight loss at different doses, and our BMI calculator to check 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.
Can I get weight loss injections free on the NHS?
Yes, if you meet eligibility criteria and are referred to a specialist tier 3 weight management service by your GP. However, NHS access is limited by long waiting lists and regional availability. Many areas have waiting times of 18+ months. Private prescriptions are often more accessible and available without NHS referral.
What is the difference between Wegovy and Ozempic?
Both contain semaglutide, but Wegovy (2.4 mg) is specifically licensed for weight management, while Ozempic (up to 2 mg) is approved for type 2 diabetes. Using Ozempic for weight loss is off-label and not NHS-licensed for weight management. Always ask your prescriber which medication they are prescribing.
How much weight can I expect to lose with these injections?
Clinical trials show average weight loss of 15–21% of body weight depending on the medication and dose. However, individual results vary significantly. Weight loss requires the injection alongside a reduced-calorie diet and increased physical activity. These medications support weight management but are not a standalone solution.
What are the side effects of weight loss injections?
Very common side effects include nausea, diarrhoea, vomiting, and constipation, particularly when starting or increasing doses. These often improve over time. Less common side effects include fatigue, dizziness, and hair loss. Seek immediate medical attention for severe stomach pain, allergic reactions, or gallbladder problems.
How do I check if I'm eligible for weight loss injections?
First, use our free BMI calculator to check your starting BMI. If your BMI is 30 or above, or 27–29.9 with a weight-related health condition, discuss weight loss options with your GP. They can refer you to specialist services and discuss whether prescription medication is appropriate for 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.