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
Diet Injections Names — How to Get in the UK
Weight loss injections, commonly called "diet jabs" or "slimming injections" in the UK, are prescription-only medications that can help support weight management. The main names you'll encounter are Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). These are GLP-1 receptor agonists or dual GIP/GLP-1 agonists — all licensed by the MHRA for weight management in adults. Getting access depends on meeting eligibility criteria and choosing between NHS specialist services or private online prescribing. This guide explains your options.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 weight loss injections if:
- You have a BMI of 30 kg/m² or above (obesity), OR
- You have a BMI of 27–29.9 kg/m² with at least one weight-related health condition such as type 2 diabetes, prediabetes, high blood pressure, abnormal blood fats, obstructive sleep apnoea, or cardiovascular disease
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds — eligibility may start at BMI 27.5 or above, as these groups face higher health risks at lower weights.
Check your personal BMI using our free BMI calculator above. You cannot take weight loss injections if you are under 18, pregnant, breastfeeding, or allergic to any ingredient. Your GP or a licensed prescriber will assess your individual suitability 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.
Two Routes to Access Weight Loss Injections
NHS route: Ask your GP for a referral to your local tier 3 specialist weight management service. Assessment and prescription happen through the NHS specialist team. Availability varies significantly by region — waiting lists can be several months or longer in many areas.
Private route: Use an online consultation with a UK-licensed prescriber through a GPhC-registered pharmacy. This is faster (often within days) and doesn't require an NHS referral. The prescriber reviews your health history online, and if appropriate, issues a prescription. Try our GLP-1 weight loss calculator to explore potential outcomes at different doses before consulting.
- 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 are the most common weight loss injection names in the UK?
The three main names are Mounjaro (tirzepatide, a dual GIP/GLP-1 agonist), Wegovy (semaglutide, a GLP-1 agonist), and Saxenda (liraglutide, a GLP-1 agonist). All are prescription-only. Mounjaro and Wegovy are once-weekly injections; Saxenda is a daily injection. Your prescriber will assess which is most suitable for you.
How do I know if I'm eligible for weight loss injections?
You need a BMI of 30 or above, or 27–29.9 with weight-related health conditions like diabetes, high blood pressure, or sleep apnoea. Ethnicity-adjusted thresholds apply for certain groups. Use our BMI calculator to check your BMI, then discuss eligibility with your GP or a licensed prescriber during a consultation.
What's the difference between NHS and private access?
NHS access requires a GP referral to a specialist weight management service — it's free but waiting lists vary (sometimes months). Private access is through online consultation with a licensed prescriber; it's faster (days) but costs between £129–£320 monthly. Both require clinical assessment; both are safe and legitimate routes.
How long does a private online consultation take?
Most online consultations take 10–20 minutes. You'll answer health questions, confirm no contraindications, and provide blood pressure/weight information. The prescriber issues a prescription if appropriate, which is then dispensed by a registered pharmacy. Results are often available within 24 hours.
Can I switch between injections or change my dose?
Yes, but only under clinical guidance. Your prescriber may adjust your dose based on tolerance and results, or recommend switching to a different injection if needed. Doses are typically increased every 4 weeks. Never change doses or switch medications without speaking to your prescriber first — they'll monitor you closely throughout treatment.
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.