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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Pharmacy Weight Loss Injections in the UK
Weight loss injections are prescription medications available through pharmacies in the UK for eligible adults. These medications, including Mounjaro and Wegovy, work by reducing appetite and supporting weight management alongside diet and exercise. This guide explains how they work, who qualifies for treatment, and how to access them through the NHS or private prescribers. Individual results vary, and a clinical assessment is always required before prescription.
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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 Injection Options
Three prescription weight loss injections are currently licensed for use in the UK. Mounjaro (tirzepatide) is a once-weekly dual GIP and GLP-1 receptor agonist that may help reduce appetite and support weight management. Clinical trials showed participants lost an average of 15–21% of their body weight, though results vary. Wegovy (semaglutide) is also a once-weekly injection that activates GLP-1 pathways, with average weight loss of around 15% in clinical trials. Saxenda (liraglutide) is a daily injection option with slightly lower efficacy but remains effective for some adults.
All three are prescription-only medicines requiring a clinical assessment before being dispensed. Eligibility typically includes adults with a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or cardiovascular disease. For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply.
Try our free GLP-1 weight loss calculator to see projected weight loss at different doses, and use our BMI calculator to check if you might be eligible for treatment.
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 in the UK
NHS access is through specialist tier 3 weight management services, typically requiring a GP referral. However, availability varies significantly by region, and waiting lists can be lengthy—some areas have several-month delays. Your GP can discuss whether NHS referral is appropriate.
Private access is available through GPhC-registered online pharmacies. Following an online consultation with a UK-licensed prescriber, a prescription is issued if clinically suitable. This route typically offers faster access without NHS waiting lists, though costs vary by dose and provider—usually £129–£320 per month.
Whichever route you choose, weight loss medications work best with a reduced-calorie diet and increased physical activity. Track your progress using our free progress tracker to monitor results over time.
- 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 do weight loss injections do?
Weight loss injections like Mounjaro and Wegovy contain medications that activate GLP-1 or GIP/GLP-1 pathways in your body. These help reduce appetite, increase feelings of fullness, and slow stomach emptying. They work alongside diet and exercise—they're not a substitute for lifestyle changes.
Am I eligible for weight loss injection therapy in the UK?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. South Asian, Chinese, Black African, or Black Caribbean adults may qualify at lower BMI thresholds. A prescriber will assess your individual suitability during a clinical consultation.
How much weight will I lose with pharmacy weight loss injections?
In clinical trials, Mounjaro helped patients lose an average of 15–21% of body weight, and Wegovy around 15%—but individual results vary significantly. Some people lose more, others less. Weight loss depends on your starting weight, adherence to injections, diet, exercise, and individual metabolism. Use our weight loss calculator for a personalised estimate.
Can I get weight loss injections on the NHS in the UK?
Yes, weight loss injections are available on the NHS through specialist tier 3 weight management services. You'll need a GP referral, and eligibility criteria must be met. However, availability and waiting times vary considerably by region—some areas have short waits, others several months. Ask your GP whether you're eligible and if referral is available in your area.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, while Wegovy (semaglutide) is a GLP-1-only agonist. Mounjaro's dual action may offer slightly stronger appetite suppression; clinical trial data suggests marginally higher average weight loss. Both are once-weekly injections. Your prescriber will advise which is more 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.