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 in the UK — Your Prescription Guide
If you're looking to buy a weight loss injection in the UK, you need to know that prescription weight management options are available through both the NHS and private prescribing. These medications—known as GLP-1 receptor agonists and dual hormone agonists—are prescription-only medicines requiring a clinical assessment from a licensed healthcare professional. This guide explains what's available, who's eligible, and how to access weight loss medication through the UK health system. Use our free BMI calculator above to check your starting point, and explore your options with your GP.
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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.
UK-Licensed Weight Loss Injections and How They Work
Three prescription weight loss injections are currently licensed for weight management uk adults:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist administered once weekly, with clinical trials showing average weight loss of 15–21% body weight over 72 weeks
- Wegovy (semaglutide) — a GLP-1 receptor agonist injected once weekly, with evidence suggesting average weight loss of approximately 15% body weight
- Saxenda (liraglutide) — a GLP-1 injection given daily, typically resulting in modest but sustainable weight loss
All three medications work by regulating appetite hormones and helping you feel fuller after smaller meals. They're used alongside a reduced-calorie diet and increased physical activity—medication alone isn't sufficient for weight loss. Individual results vary considerably, and a prescriber will assess whether any of these options suit your specific health profile before issuing a prescription.
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 and Eligibility
In the UK, you can access prescription weight loss medication through either the NHS or private prescribing routes. NHS access is through tier 3 specialist weight management services—your GP can refer you, though waiting lists vary significantly by region and availability can be limited. Private access involves an online clinical assessment with a UK-licensed prescriber; if approved, the prescription is dispensed by a regulated pharmacy without needing an NHS referral.
To be eligible, you typically need a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, hypertension, or cardiovascular disease. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may qualify at lower BMI thresholds due to higher health risks. Your GP or a prescriber will assess whether prescription weight loss medication is appropriate for you. Try our GLP-1 weight loss calculator to see potential outcomes, and use the weight converter to track your progress in familiar UK measurements.
- 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.
What's the difference between Mounjaro and Wegovy?
Both are once-weekly injections licensed for weight management in the UK. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, while Wegovy (semaglutide) activates only the GLP-1 pathway. Clinical trials show similar average weight loss ranges (15–21%), though individual responses vary. Your prescriber will recommend the most suitable option based on your health profile.
Can I get weight loss injections on the NHS?
Yes, through specialist tier 3 weight management services. Your GP can refer you, but access and waiting times vary significantly by region. Private prescribing is also available without an NHS referral, following an online clinical assessment with a licensed prescriber.
Who is eligible for prescription weight loss medication?
You typically need a BMI of 30 or above, or 27–29.9 with weight-related health conditions like diabetes, high blood pressure, or heart disease. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may qualify at lower BMIs. A healthcare professional will assess your individual eligibility.
Are weight loss injections safe?
Prescription weight loss medications are regulated by the MHRA and approved for safe use in the UK when prescribed appropriately. Common side effects include nausea and changes in digestion. Serious side effects are rare but can occur. Your prescriber will discuss risks and benefits, and you should report any concerns to them immediately.
How much weight can I expect to lose?
Clinical trials show average weight loss of 15–21% for Mounjaro and approximately 15% for Wegovy—but individual results vary significantly. Weight loss depends on the dose, your adherence to medication and lifestyle changes, and your personal metabolism. A prescriber can discuss realistic expectations based on your circumstances using our free weight loss calculator.
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.