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
Free tracker included with every download this week
What is Injection Fat Reduction?
Injection fat reduction refers to prescription weight loss medications delivered by weekly injection. In the UK, these are primarily GLP-1 receptor agonist medicines like Wegovy (semaglutide) and Mounjaro (tirzepatide), which may help reduce appetite and support weight loss when combined with lifestyle changes. These are serious prescription medications requiring clinical assessment, not cosmetic fat-dissolving treatments. NHS guidance supports their use for eligible adults alongside diet and physical activity.
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Calculate Your BMI Instantly
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 Weight Loss Injections Work
Prescription weight loss injections work by mimicking natural hormones that regulate appetite and blood sugar. Wegovy (semaglutide) is a GLP-1 receptor agonist that signals fullness to the brain, slows stomach emptying, and reduces food cravings. Mounjaro (tirzepatide) works similarly but activates both GIP and GLP-1 pathways, offering dual hormone activation.
In clinical trials, Wegovy helped participants lose an average of 15% of body weight over 68 weeks, whilst Mounjaro showed average losses of 15–21% depending on dose. These results were achieved alongside a reduced-calorie diet and increased physical activity — medication alone is not effective without lifestyle changes.
You can estimate potential weight loss outcomes using our free GLP-1 weight loss calculator, which projects results at different doses. All injections are once-weekly and prescribed following a clinical assessment by a UK-licensed prescriber.
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.
UK Eligibility and How to Access
In the UK, weight loss injections may be prescribed for adults with a BMI of 30 or above, or BMI of 27–29 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may be eligible at lower BMI thresholds due to higher health risks at these levels.
Access is available through NHS specialist weight management services (tier 3) or private prescribing via online consultation with a UK-licensed prescriber. NHS waiting lists vary significantly by region. Calculate your personal BMI using our free BMI calculator to check where you fall, then discuss eligibility with your GP or a licensed healthcare professional.
- 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 weight loss injections the same as cosmetic fat-dissolving injections?
No. Prescription weight loss injections like Wegovy and Mounjaro are systemic medicines that work through hormone pathways. They are not cosmetic procedures. Fat-dissolving cosmetic injections (like aqualyx) are entirely different treatments administered by aestheticians.
Is Ozempic used for weight loss in the UK?
Ozempic contains semaglutide but is licensed for type 2 diabetes only — not weight loss. Wegovy is the licensed weight management version of semaglutide. Using Ozempic for weight loss is off-label and not recommended by NHS guidance.
How quickly will I lose weight with injections?
Weight loss varies significantly between individuals. Clinical trials show average losses of 15–21% over several months, but results depend on dose, diet adherence, and physical activity. Sustainable loss typically occurs at 0.5–1 kg per week.
Can I get weight loss injections on the NHS?
Yes, but access is through specialist tier 3 weight management services following GP referral. Availability and waiting times vary by region. Private access is available through licensed online prescribers without NHS referral.
What happens if I stop taking the injection?
Weight regain often occurs when stopping medication, particularly if lifestyle changes are not maintained. These medications support weight loss — they do not supports obesity. Long-term use alongside diet and exercise offers better sustained results.
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.