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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Diet Injections Names — UK-Licensed Weight Loss Options
If you're considering prescription weight loss injections in the UK, you'll encounter three main options: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These prescription slimming injections work by mimicking natural hormones that regulate appetite and blood sugar. All three are licensed for weight management in UK adults, but they differ in mechanism, injection frequency, and clinical evidence. Understanding which options exist — and how they work — is the first step in discussing weight loss treatment with your GP or a licensed prescriber. This guide covers all available diet injections names, how they compare, and how to access them through NHS or private routes.
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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 Diet Injections: Names, Types, and How They Work
Three prescription medications are currently licensed in the UK specifically for weight management:
- Mounjaro (tirzepatide) — A once-weekly injection that activates both GIP and GLP-1 hormone pathways. Starting dose 2.5mg, maximum 15mg weekly. Clinical trials (SURMOUNT-1) showed average weight loss of 15–21% body weight depending on dose, achieved alongside reduced-calorie diet and increased physical activity.
- Wegovy (semaglutide) — A once-weekly GLP-1 injection starting at 0.25mg, escalating to maximum 2.4mg weekly. STEP-1 trial data showed approximately 15% average body weight loss. Note: Ozempic is also semaglutide but licensed for diabetes, not weight management in the UK.
- Saxenda (liraglutide) — A daily GLP-1 injection (not weekly like the others), dosed from 0.6mg to 3mg daily. Clinical evidence supports modest weight loss, though Mounjaro and Wegovy are now more commonly prescribed.
All three are prescription-only medicines requiring individual clinical assessment before dispensing. Individual results vary significantly — these percentages represent clinical trial averages, not assured outcomes.
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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.
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Accessing Diet Injections in the UK: NHS vs Private Routes
NHS access: Weight loss injections are available through tier 3 specialist weight management services, typically accessed via GP referral. NICE has approved tirzepatide (Mounjaro) within NHS services, though regional availability varies significantly and waiting lists can be lengthy in many areas.
Private access: All three medications are available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber. This route does not require NHS referral. Eligibility criteria for prescription weight loss treatment generally require a BMI of 30 or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, cardiovascular disease, sleep apnoea). For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds may apply. Our free GLP-1 weight loss calculator can help you estimate potential outcomes at different doses. Always consult your GP or a prescriber to confirm eligibility for your individual circumstances.
- 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?
Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) activates GLP-1 only. Mounjaro is injected once weekly starting at 2.5mg up to 15mg, and clinical trials showed slightly higher average weight loss (up to 21%) compared to Wegovy's 15%. Both are prescription-only and require clinical assessment.
Can I get diet injections through the NHS?
Yes, through tier 3 specialist weight management services following GP referral. However, NHS availability and waiting times vary significantly by region (ICB). Private online prescribing offers faster access without NHS referral, provided you meet clinical eligibility criteria and have a consultation with a UK-licensed prescriber.
What is Saxenda and how does it compare?
Saxenda (liraglutide) is a daily GLP-1 injection approved for weight management in the UK. Unlike Mounjaro and Wegovy (both weekly), Saxenda requires daily injections. It remains available but Mounjaro and Wegovy are now more commonly prescribed due to once-weekly dosing and stronger clinical trial results.
Are all diet injections prescription-only?
Yes, all UK-licensed weight loss injections (Mounjaro, Wegovy, Saxenda) are prescription-only medicines. They cannot be purchased without a prescription from a UK-licensed prescriber, whether through the NHS or private online services. Any provider claiming otherwise is operating illegally.
How do I know which diet injection is right for me?
A licensed prescriber assesses your individual health, medical history, BMI, and any comorbidities to determine suitability. Use our free BMI calculator to check your current BMI and understand whether you fall into eligible ranges. Your GP or online prescriber will then discuss which option — Mounjaro, Wegovy, or Saxenda — is most 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.