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 Diet Injections in the UK
Weight loss injections, commonly called slimming injections or fat jabs in the UK, are prescription medications that can support weight management. There are two main routes to access them: through the NHS via specialist services, or privately through online consultations. This guide explains eligibility criteria, both pathways, and what happens during the assessment process so you can understand your options.
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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 Weight Loss Injections
You may be eligible for prescription slimming injections if you meet one of these criteria:
- BMI of 30 kg/m² or above (obesity), OR
- BMI of 27–29.9 kg/m² with at least one weight-related health condition
Common qualifying health conditions include type 2 diabetes, prediabetes, high blood pressure, abnormal cholesterol levels, obstructive sleep apnoea, and cardiovascular disease history.
Ethnicity-adjusted thresholds: If you are of South Asian, Chinese, Black African, or Black Caribbean heritage, NHS guidelines recommend lower BMI thresholds — you may qualify from BMI 27.5 or above. This is because these populations face higher health risks at lower BMI levels.
Use our free BMI calculator above to check your personal BMI, then discuss eligibility with your GP or a licensed prescriber. You cannot get weight loss injections if you are under 18, pregnant, breastfeeding, or have certain medical conditions — a clinical assessment will determine this.
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: Ask your GP for a referral to your local tier 3 weight management service. These are specialist clinics that offer comprehensive weight management support. If you qualify, a specialist team will assess you and may prescribe GLP-1 weight loss injections. However, NHS waiting lists vary significantly by region and can take several months to years in some areas.
Private Route: You can access weight loss injections through a GPhC-registered online pharmacy following an online consultation with a UK-licensed prescriber. This is faster — typically available within days — and doesn't require an NHS referral. A prescriber will assess your health via questionnaire and video call, then issue a prescription if appropriate. Costs typically range from £129–£320 monthly depending on the medication and dose.
- 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 happens during a weight loss injection consultation?
A prescriber or specialist will review your medical history, current medications, and health conditions via a questionnaire or appointment. They'll check your BMI, discuss weight loss goals, and assess whether you're suitable for the medication. If approved, you'll receive a prescription to be dispensed by a registered pharmacy.
Can I get weight loss injections on the NHS without waiting months?
NHS waiting times vary by region. Some areas have shorter lists, others can take 6–12+ months. If you need treatment sooner, private online consultations typically provide access within days, though you'll pay for the medication yourself.
Are Mounjaro and Wegovy the only weight loss injection options?
In the UK, the main prescription weight loss injections are Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Mounjaro and Wegovy are once-weekly injections. All require a prescription and clinical assessment. Try our GLP-1 weight loss calculator to understand how these medications work with lifestyle changes.
What if I don't meet the BMI threshold but have weight-related health problems?
If your BMI is between 27–29.9 kg/m², you may still qualify if you have a weight-related condition like diabetes, high blood pressure, or sleep apnoea. A GP or prescriber can assess whether you meet the criteria during a consultation.
Do I need to do anything before my consultation?
Have your current weight and height ready so your BMI can be calculated. Note any medications you take, allergies, and health conditions. If applying for NHS services, your GP can provide referral information. Use the weight converter on this page if you need to switch between stone, pounds, and kilograms.
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.