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 Reviews UK — What Are Your Options?
Weight loss injections are prescription-only medications that can help with weight management when used alongside diet and exercise changes. In the UK, three main options are licensed for adults: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). This guide reviews each option, explains UK eligibility criteria, and covers how to access them through the NHS or privately. If you're considering prescription weight loss medication, understanding your options and how to discuss them with your GP is the first step.
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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
Mounjaro (tirzepatide) is a once-weekly injection that works as a dual GIP and GLP-1 receptor agonist. Clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks, though individual results vary significantly. It starts at 2.5mg and titrates to a maximum of 15mg weekly.
Wegovy (semaglutide) is also a once-weekly injection but uses a single GLP-1 mechanism. The STEP-1 trial showed average weight loss of around 15% body weight at the maximum 2.4mg dose. It's stepped from 0.25mg upwards over several weeks.
Saxenda (liraglutide) is a daily injection (not weekly) with doses ranging from 0.6mg to 3mg daily. Clinical evidence supports modest but meaningful weight loss in most users.
All three are prescription-only and require a clinical assessment before being prescribed. Which medication is suitable depends on your individual health, medical history, and preferences discussed with a prescriber.
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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.
NHS vs Private Access and How to Get Started
NHS access: Weight loss injections are available through NHS specialist tier 3 weight management services, but only after GP referral. Availability varies significantly by region, and waiting lists can be lengthy in many areas. Your GP can advise whether you meet local eligibility criteria and how to request a referral.
Private access: All three medications are available through GPhC-registered online prescribing services. You'll complete an online clinical assessment with a UK-licensed prescriber, and if appropriate, receive a prescription. This route doesn't require NHS referral and can be faster, though you'll pay privately (typically £129–£320 per month depending on dose).
Next step: Speak to your GP about whether prescription weight loss medication might suit your circumstances. They can discuss your health, assess your BMI using our free BMI calculator, and guide you towards NHS specialist services or private options.
- 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.
Am I eligible for weight loss injections in the UK?
UK eligibility generally requires a BMI of 30 or above, or 27–29.9 with a weight-related health condition (such as type 2 diabetes, high blood pressure, or sleep apnoea). South Asian, Chinese, Black African, and Black Caribbean adults may qualify at lower BMI thresholds. Your GP or a licensed prescriber will assess your individual circumstances. Use our free BMI calculator above to check your starting point.
How much weight will I lose with weight loss injections?
Clinical trials show average weight loss of 15–21% body weight with Mounjaro and around 15% with Wegovy, achieved alongside reduced-calorie diet and increased physical activity. However, individual results vary considerably. Some people lose more, some less. Weight loss is not assured, and a prescriber will discuss realistic expectations based on your health profile.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) uses a dual GIP and GLP-1 mechanism and is injected once weekly. Wegovy (semaglutide) uses a single GLP-1 mechanism, also once weekly. Mounjaro typically showed slightly higher average weight loss in trials, but both are effective. Your prescriber will recommend the most suitable option for you based on your medical history and preferences.
Can I get weight loss injections on the NHS?
Yes, weight loss injections are available through NHS specialist weight management services (tier 3), but you'll need a GP referral and will typically be assessed for eligibility based on your BMI and health conditions. NHS availability and waiting times vary by region. Private access is faster but costs money. Discuss both options with your GP.
Are weight loss injections safe?
All three UK-licensed options have been through rigorous clinical trials and safety monitoring. Common side effects include nausea, diarrhoea, and constipation — usually mild and temporary. Serious side effects are rare. A prescriber will review your medical history to ensure the medication is safe for you personally and will monitor you during treatment.
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.