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 Slimming Injections in the UK
Slimming injections—also known as weight loss injections or GLP-1 jabs—are prescription-only medications available through two main routes in the UK: the NHS and private prescription services. This guide explains eligibility criteria, how each route works, what to expect during a consultation, and the key differences between accessing treatment publicly and privately. Whether you're interested in prescription slimming injections for health reasons or want to understand your options, this practical overview will help you navigate the process.
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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 and BMI Thresholds
To access weight loss injections in the UK, you must meet specific eligibility criteria based on your BMI and health conditions. The standard threshold is a BMI of 30 kg/m² or above (obesity category). If your BMI is between 27 and 29.9 (overweight range), you may still be eligible if you have at least one weight-related health condition.
Qualifying health conditions include:
- Type 2 diabetes or prediabetes
- High blood pressure (hypertension)
- Abnormal blood fats (dyslipidaemia)
- Obstructive sleep apnoea
- Cardiovascular disease history
If you are of South Asian, Chinese, Black African, or Black Caribbean background, the NHS recommends lower BMI thresholds—eligibility may start at BMI 27.5 or above because these groups face higher health risks at lower weights. Use our free BMI calculator above to check your personal BMI instantly and see where you fall on the NHS classifications. A prescriber will assess your individual health profile during a consultation.
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 Routes: How to Access Treatment
There are two ways to access weight loss injections in the UK: through the NHS or via private prescription. The NHS route involves asking your GP for a referral to a specialist tier 3 weight management service. However, NHS availability varies significantly by region, and waiting lists can be very long—often months or even years in some areas. Once referred, the specialist team will assess you and prescribe if appropriate.
The private route is faster: you complete an online consultation with a UK-licensed prescriber (no GP referral needed), and if approved, a GPhC-registered pharmacy dispenses the medication. Private access typically costs £129–£320 per month depending on dose. Both routes require a clinical assessment—prescribers will not issue prescriptions without evaluating your health, BMI, and suitability.
- 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 should I expect during a prescription consultation for slimming injections?
A prescriber will ask about your medical history, current medications, weight, height (to calculate BMI), and any weight-related health conditions. They'll discuss how the medication works, expected side effects, and whether it's suitable for you. Be honest about your health—this helps them make the safest decision. The consultation usually takes 15–30 minutes online or by phone.
How quickly can I start slimming injections through the NHS?
NHS timelines vary by region. Your GP first refers you to a tier 3 weight management service, which may take weeks. Then you join a waiting list for the specialist team, which can be months or longer depending on your local integrated care board (ICB). Private routes are typically much faster—prescription and first dose within days to weeks.
Can I use my current medications with weight loss injections?
Most medications are compatible, but some—particularly oral contraceptives and certain diabetes drugs—may need adjustment. Always tell your prescriber about every medication and supplement you take. They'll assess interactions and may recommend timing changes or alternative contraception methods.
What happens if I'm not eligible for slimming injections?
If your BMI is under 27 or you don't have qualifying health conditions, a prescriber may suggest other approaches: structured dietary support, physical activity programmes, or NHS-funded tier 1 and tier 2 weight management services. Your GP can discuss all available options tailored to your circumstances.
How do I start the NHS referral process for weight loss injections?
Book an appointment with your GP and explain that you're interested in specialist weight management treatment. They'll assess your suitability and refer you to your local tier 3 weight management service if appropriate. Ask about waiting times in your area—availability differs by region. Our free GLP-1 weight loss calculator can help you understand potential outcomes while you wait.
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.