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
How to Get Diet Injections in the UK
Weight loss injections, commonly known as fat jabs or slimming injections, are now available in the UK through two distinct pathways: NHS specialist services and private online consultations. These prescription-only medications — including GLP-1 weight loss options and dual-action alternatives — can help support weight management alongside diet and exercise. Whether you're eligible depends on your BMI and health conditions. This guide explains both routes, eligibility criteria, and what to expect from the consultation process, helping you understand your options for accessing these treatments in the UK.
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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.
Eligibility Criteria for Diet Injections
To access weight loss injections in the UK, you must meet specific eligibility criteria set by MHRA-licensed medicines and NHS guidance.
- BMI 30 or above: Adults with a BMI of 30 kg/m² or higher qualify regardless of other health conditions
- BMI 27–29.9 with qualifying health conditions: Overweight adults may be eligible if they have type 2 diabetes, prediabetes, high blood pressure, abnormal blood fats, obstructive sleep apnoea, or cardiovascular disease history
- Ethnicity adjustments: For South Asian, Chinese, Black African, and Black Caribbean adults, lower BMI thresholds apply — eligibility may start at BMI 27.5 or above due to higher health risks at lower weights
- Age requirement: Must be 18 years or older; not suitable for pregnant, breastfeeding, or those with certain medical conditions
Use our free BMI calculator above to check your starting point instantly. Your personal BMI helps determine which pathway may be most suitable for you.
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: NHS vs Private Access
NHS route: Referral from your GP to a tier 3 specialist weight management service. This is free but involves waiting lists — typically weeks to months in some regions, longer in others. Access varies significantly across ICBs (Integrated Care Boards). The NHS multidisciplinary team provides comprehensive support including dietitian advice and behavioural coaching.
Private route: Online consultation with a UK-licensed prescriber through a GPhC-registered pharmacy. Faster access (often within days), no NHS referral required, but costs approximately £129–£320 monthly depending on dose. Both routes require a clinical assessment before prescription. Try our GLP-1 weight loss calculator to explore potential outcomes with different dosing protocols.
- 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 are prescription-only medicines that use GLP-1 receptor agonist technology — or dual GIP/GLP-1 mechanisms — to help regulate appetite, reduce food cravings, and support feeling fuller after meals. They're administered as once-weekly injections and work alongside reduced-calorie diet and physical activity for best results.
Do I need to see my GP first to get a weight loss injection?
Not necessarily. For NHS access, yes — you'll need a GP referral to specialist tier 3 services. For private access, you can book a direct online consultation with a licensed prescriber without GP involvement. Either way, a clinical assessment is required to confirm suitability.
How long does the private consultation process take?
Private online consultations typically take 15–30 minutes. You'll answer questions about your medical history, current medications, weight, height, and health conditions. The prescriber assesses suitability and, if approved, issues a prescription to be dispensed by a GPhC-registered pharmacy — often within 24–48 hours.
What weight-related health conditions qualify me for weight loss injections?
Qualifying conditions include type 2 diabetes or prediabetes, high blood pressure (hypertension), abnormal blood fats (dyslipidaemia), obstructive sleep apnoea, and cardiovascular disease history. If you have a BMI of 30 or above, additional conditions are not required.
Can I get diet injections if I'm on other medications?
Most medications are compatible, but some require adjustment — particularly diabetes medications, oral contraceptives, and certain other drugs. Your prescriber will review all your current medications during the consultation and advise accordingly. Always inform them of everything you take.
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.