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 The Weight Loss Injection Called?
Weight loss injections are prescription-only medicines that help support weight management in UK adults. The most commonly prescribed options are Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are GLP-1 receptor agonist medications — sometimes called "slimming injections" in the media — that work by helping to regulate appetite and support feeling fuller after meals. They're available through the NHS and private prescribing in the UK, depending on your eligibility and local services. This guide explains what they're called, how they work, and how to find out if prescription weight loss medication is right for you.
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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.
UK-Licensed Weight Loss Injections Explained
Three prescription-only weight loss injections are currently licensed in the UK for weight management. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — a newer type of medication that activates two natural hormone pathways to help regulate appetite and support weight loss. Wegovy (semaglutide) is a GLP-1 receptor agonist, a once-weekly injection administered by you at home. Saxenda (liraglutide) is also a GLP-1 agonist but requires daily injections rather than weekly. Clinical trials show these medications help adults lose an average of 15–21% of their body weight when combined with a reduced-calorie diet and increased physical activity — though individual results vary significantly. You can calculate your potential weight loss using our free GLP-1 weight loss calculator. All three are prescription-only and require a clinical assessment before being prescribed, either through NHS specialist weight management services or private online prescribers.
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 and How to Check Eligibility
Access to weight loss injections in the UK depends on your BMI, health conditions, and whether you use NHS or private services. NHS access is through specialist tier 3 weight management services — your GP can refer you, though waiting times vary significantly by region and can be lengthy. Private access is available through UK-licensed online prescribers following a clinical consultation. To check if you might be eligible, calculate your BMI using our free BMI calculator above. You may qualify if your BMI is 30 or above, or 27 or above with weight-related conditions like type 2 diabetes, high blood pressure, or cardiovascular disease. Lower thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Your GP can discuss which option is best for your situation and refer you to appropriate services.
- 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.
Is the weight loss injection the same as Ozempic?
No. Ozempic contains semaglutide but is licensed for type 2 diabetes management in the UK. Wegovy also contains semaglutide but at a higher dose and is specifically licensed for weight management. Using Ozempic for weight loss is off-label and not recommended. Wegovy is the correct licensed option for weight loss in the UK.
Can I get weight loss injections on the NHS?
Yes, but access varies significantly by region. You'll need referral to a specialist tier 3 weight management service from your GP. NICE has approved tirzepatide (Mounjaro) for NHS use, but availability depends on your local integrated care board and current waiting lists, which can be several months to years in some areas.
How much do weight loss injections cost privately in the UK?
Private costs typically range from £129 to £320 per month depending on the medication and dose. Mounjaro and Wegovy start at lower doses and increase over several weeks, so initial costs may be lower. Always check the total cost of the full treatment course with your provider.
Do weight loss injections work without diet and exercise?
No. Clinical trials show that weight loss injections work best when combined with a reduced-calorie diet and increased physical activity. The medication supports these lifestyle changes but is not a substitute for them. Long-term success requires sustained dietary and activity changes.
Who cannot take weight loss injections?
Weight loss injections are not suitable for pregnant or breastfeeding women, people under 18, those with a history of thyroid cancer or medullary thyroid carcinoma, or people with severe gastric disorders. Your prescriber will assess your full medical history before determining eligibility.
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.