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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How to Get Fat Injections on the NHS
Weight loss injections—commonly called "fat jabs" or "slimming injections"—are now available on the NHS for eligible adults. These prescription medicines can support weight management alongside diet and exercise. However, NHS access works differently from private prescription routes, and availability varies by region. This guide explains the eligibility criteria, how the NHS pathway works, and what to expect from your GP referral and specialist assessment.
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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.
NHS Eligibility Criteria for Weight Loss Injections
To access weight loss injections on the NHS, you must meet specific eligibility thresholds and be assessed by a specialist tier 3 weight management service. BMI requirements are:
- BMI of 30 or above (obesity), OR
- BMI of 27–29.9 (overweight) with at least one weight-related health condition
If you are of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply: eligible from BMI 27.5 or above, because these populations have higher risk of type 2 diabetes and cardiovascular disease at lower weights.
Qualifying health conditions include: type 2 diabetes or prediabetes, high blood pressure, abnormal blood fats, obstructive sleep apnoea, or history of cardiovascular disease. You must be 18 or over, not pregnant, and not breastfeeding. Use our free BMI calculator above to check where you fall on the NHS eligibility scale.
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.
Two Routes to Access: NHS vs Private
The NHS route involves referral from your GP to a tier 3 specialist weight management service. Your GP will assess your eligibility, take your medical history, and make a referral if appropriate. However, NHS specialist services have significant waiting lists—often 6–12 months or longer depending on your region. Once seen, the specialist team will decide whether prescription injections like Mounjaro or Wegovy are right for you.
The private route is faster. You complete an online consultation with a UK-licensed prescriber, provide your medical history, and receive a prescription if clinically suitable. This typically takes 24–48 hours. Private costs range from £129–£320 monthly depending on dose. Both routes require genuine clinical assessment—neither route is "instant access." Track your progress once started using our free progress tracker.
- 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 is the actual difference between NHS and private weight loss injections?
The medication (e.g. Mounjaro or Wegovy) is the same regardless of route. The difference is speed and cost. NHS is free but involves waiting lists and tier 3 referral requirements. Private is faster (24–48 hours) but costs £129–£320 per month. Both require proper clinical assessment and cannot diagnose or prescribe without one.
Can my GP prescribe slimming injections directly?
Not typically. GPs cannot routinely prescribe weight loss injections. You must be referred to a tier 3 specialist weight management service, where the specialist team assesses you and decides whether the medication is appropriate. This is NHS policy to ensure safe, monitored use.
I have a BMI of 28. Am I eligible for NHS weight loss injections?
You may be eligible if you have a qualifying health condition (type 2 diabetes, high blood pressure, sleep apnoea, etc.). If you are of South Asian, Chinese, Black African, or Black Caribbean heritage, you may be eligible from BMI 27.5. Check with your GP about your specific circumstances. Our free BMI calculator can help you check your BMI category.
How long are NHS waiting lists for weight management services?
This varies significantly by region and NHS ICB (Integrated Care Board). Some areas have waiting lists of 6–8 months; others may be 12+ months. Ask your GP for a referral and they will advise you of the expected wait time in your local area.
What happens during a private weight loss injection consultation?
You complete an online form covering your medical history, weight, height, blood pressure (if you can measure it), and any medications. The prescriber reviews this and may ask follow-up questions. If appropriate, they issue a prescription and arrange dispensing by a GPhC-registered pharmacy. This is a genuine clinical assessment, not a quick approval process.
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.