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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Fat Burner Shots — What You Need to Know
Fat burner shots — sometimes called weight loss injections or slimming jabs — are prescription-only medications that help reduce appetite and support weight management. In the UK, the most commonly discussed fat burner shots are GLP-1 receptor agonist medications like Mounjaro and Wegovy, which are licensed for weight management in adults with a BMI of 30 or above, or 27 or above with weight-related health conditions. This guide explains how they work, UK access routes, and what the NHS health advice says about sustainable weight loss.
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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 Fat Burner Shots Work in the UK
Fat burner shots are injectable medications that use hormone-mimicking technology to support weight loss. The most widely discussed options in the UK are dual GIP/GLP-1 receptor agonists (like Mounjaro) and GLP-1 receptor agonists (like Wegovy). These medications work by activating natural pathways in the body that regulate appetite, reduce food cravings, and help you feel fuller after smaller meals. They also slow how quickly food leaves the stomach, which contributes to prolonged satiety. Unlike metabolism-boosting claims sometimes made about non-prescription "fat burner" supplements, these prescription injections have clinical evidence behind them. The SURMOUNT clinical trials showed that Mounjaro helped participants lose an average of 15–21% of their body weight over 72 weeks, whilst Wegovy trials showed similar average weight loss of around 15%. Individual results vary significantly, and these medications are always prescribed alongside reduced-calorie diet and increased physical activity for best results.
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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.
UK Access and NHS Guidance on Weight Management
In the UK, prescription weight loss injections are available through two main routes. NHS access is through specialist tier 3 weight management services — your GP can refer you, though waiting times vary significantly by region and availability. Private access is through online prescribing following a clinical assessment with a UK-licensed prescriber. The NHS health guidance emphasises that sustainable weight loss of 0.5–1 kg per week is safest, achieved through a calorie deficit combined with physical activity and behaviour change. Before any prescription, you'll have a clinical assessment to check whether a fat burner shot is suitable for your individual health profile. Our free BMI calculator and weight converter can help you understand your current weight status in UK measurements, and our GLP-1 weight loss calculator can show you projected results at different doses. Always speak with your GP about which approach is right for you.
- 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.
Are fat burner shots the same as Mounjaro or Wegovy?
Mounjaro and Wegovy are the most commonly prescribed fat burner shots in the UK. Mounjaro is a dual GIP/GLP-1 receptor agonist, whilst Wegovy is a GLP-1 agonist only. Both are prescription-only, once-weekly injections licensed for weight management in UK adults. There are other options like Saxenda (daily injection), but Mounjaro and Wegovy are currently most discussed in UK nhs health information and media.
Can I get fat burner shots on the NHS?
Yes, through specialist tier 3 weight management services. Your GP can refer you if you meet eligibility criteria (BMI 30+, or 27+ with weight-related health conditions). However, NHS availability varies significantly by region — some areas have long waiting lists. Private online prescribing is also available in the UK following clinical assessment with a licensed prescriber.
How quickly will I lose weight with fat burner shots?
Individual results vary, but clinical trials showed average weight loss of 15–21% of body weight over 72 weeks with Mounjaro, and around 15% with Wegovy. The NHS recommends losing 0.5–1 kg per week as a safe, sustainable rate. Results depend on your starting weight, dose, diet, physical activity, and individual metabolism — your GP or prescriber can discuss realistic expectations for you.
What are the side effects of fat burner shots?
Common side effects include nausea, diarrhoea, constipation, and stomach pain — usually mild and temporary. More serious (but rare) side effects can include gallbladder problems or pancreatitis. Always discuss potential side effects with your GP or prescriber. The NHS health information recommends reporting any concerning symptoms to your healthcare provider immediately.
Are fat burner shots better than diet and exercise alone?
Fat burner shots are most effective when combined with diet and exercise — they are not a replacement for lifestyle changes. Evidence suggests they help manage appetite and support weight loss when used alongside a reduced-calorie diet and physical activity. For some people with significant obesity or weight-related health conditions, they offer additional support beyond diet alone. Your GP can advise whether a fat burner shot is appropriate for your situation.
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.