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 a Diet Injection in the UK
Weight loss injections, commonly called diet injections or fat jabs in the UK, are prescription-only medications that may help support weight management. If you're considering this type of treatment, there are two main routes to access them: through the NHS specialist weight management services or via a private consultation with a UK-licensed prescriber. This guide explains eligibility criteria, how each route works, and what the consultation process involves so you can make an informed decision about whether this treatment is right for you.
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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.
Who Is Eligible for Weight Loss Injections?
BMI thresholds and qualifying conditions: You may be eligible for prescription weight loss injection treatment if you have a BMI of 30 kg/m² or above, or a BMI of 27–29.9 kg/m² alongside at least one weight-related health condition. Weight-related conditions that may qualify include type 2 diabetes, prediabetes, high blood pressure, abnormal blood fats, obstructive sleep apnoea, or a history of cardiovascular disease.
Ethnicity-adjusted thresholds: If you are of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower BMI thresholds. For these groups, eligibility may begin at a BMI of 27.5 or above, as these populations face higher health risks at lower BMI levels. Use our free BMI calculator above to check your personal BMI and understand where you fall on the NHS classification scale.
Age requirements: You must be at least 18 years old. Pregnant women, those planning pregnancy, and breastfeeding women are not eligible. You should not have a history of severe gastroparesis or related digestion problems.
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
NHS route: Access through the NHS involves referral from your GP to a specialist tier 3 or tier 4 weight management service. Your GP will assess your health and suitability before referring you. Availability varies significantly by region—some areas have substantial waiting lists (months to years in some cases), whilst others have shorter timescales. The NHS provides these medicines as part of specialist services, though access depends on local commissioning decisions and resource availability.
Private route: Private weight loss injections are available through GPhC-registered online pharmacies. You complete an online health consultation with a UK-licensed prescriber who reviews your medical history and assesses eligibility. If approved, a prescription is issued and the medication is dispensed by the pharmacy. Private access is faster (often within days) but requires payment. Try our free GLP-1 weight loss calculator to estimate potential outcomes and compare options before deciding on your approach.
What the consultation involves: Both NHS and private consultations assess your medical history, current medications, weight, height, and BMI. Your prescriber will discuss your weight loss goals, lifestyle factors, and any contraindications. You'll be informed about potential side effects, injection technique, and realistic expectations—individual results vary significantly, and medication is most effective alongside a reduced-calorie diet and increased physical activity. Your prescriber will recommend a starting dose and arrange follow-up appointments to monitor your progress and adjust doses if needed.
- 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 a diet injection and how does it work?
Diet injections (weight loss injections or slimming injections) are prescription-only medications that work as GLP-1 or GIP/GLP-1 receptor agonists. They mimic natural hormones that help regulate appetite, reduce food cravings, and support feeling fuller after smaller meals. Clinical trials have shown that GLP-1 weight loss medication, when combined with diet and exercise, may help support weight management—though individual results vary.
What's the difference between NHS and private weight loss injections?
NHS access involves GP referral to specialist services and is free, but waiting lists can be lengthy. Private access is through online consultations with UK-licensed prescribers and is faster but requires payment (typically £129–£320 per month depending on dose). Both routes require clinical assessment and a valid prescription from a UK-licensed healthcare professional.
How long does the private consultation process take?
Private online consultations typically take 15–30 minutes. After submission, prescribers usually review and respond within 24–48 hours. If approved, your prescription is issued and medication can be dispatched within days. NHS referral and assessment usually takes longer due to specialist service waiting lists, which vary by region.
Can I get a diet injection if my BMI is between 27 and 30?
Yes, if you have a weight-related health condition such as type 2 diabetes, high blood pressure, or cardiovascular disease. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the threshold may be lower (from BMI 27.5 or above). Your prescriber will assess your individual circumstances during consultation.
What happens after I'm prescribed a diet injection?
After prescription, you'll receive training on injection technique (usually self-administered weekly). Your prescriber will schedule follow-up appointments to monitor side effects, assess weight loss progress, and adjust doses if needed. You should track your progress alongside dietary and lifestyle changes. Use our free progress tracker to log your weight loss journey and monitor outcomes over time.
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.