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 Buy Weight Loss Injections in the UK
Weight loss injections are prescription-only medications available in the UK through both NHS specialist services and private prescribing. The most commonly prescribed options are Wegovy (semaglutide) and Mounjaro (tirzepatide), both GLP-1 receptor agonist medications licensed for weight management. These are not over-the-counter products — you'll need a clinical assessment from a licensed prescriber to determine if they're suitable for you. This guide explains your options, eligibility criteria, and how to access these medications 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.
UK Routes to Prescription Weight Loss Injections
There are two main ways to access weight loss injections in the UK: through the NHS or via private prescribing. On the NHS, you'll need referral to a tier 3 specialist weight management service, typically from your GP. Availability varies significantly by region and waiting times can be lengthy. For private access, you can consult with a UK-licensed prescriber through registered online services. A clinical assessment is required before prescription — the prescriber will review your BMI, medical history, and weight-related health conditions. Check your BMI using our free BMI calculator to see if you may be eligible. Both routes result in prescriptions dispensed by GPhC-registered pharmacies. Prescription weight loss medication costs vary by dose and provider, ranging from approximately £129–£320 monthly privately.
- NHS: referral required, free on prescription, variable waiting times
- Private: direct access, faster, costs apply, no NHS referral needed
- Both require clinical assessment by a licensed prescriber
- Medications dispensed by regulated UK pharmacies only
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.
Eligibility and What to Expect
To be eligible for weight loss injections in the UK, you typically need a BMI of 30 or above, or BMI 27–29.9 with at least one weight-related health condition (such as type 2 diabetes, high blood pressure, or cardiovascular disease). Adults of South Asian, Chinese, Black African, or Black Caribbean heritage may have lower BMI thresholds due to higher health risks at lower weights. Use our GLP-1 weight loss calculator to estimate potential results and our weight converter to check your weight in kg if needed. Once prescribed, injections are self-administered weekly at home. Clinical trials show weight loss averages around 15% of body weight with semaglutide, though individual results vary significantly. Weight loss medications work best alongside reduced-calorie diet and increased physical activity — they support weight management but are not standalone solutions.
- 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's the difference between Wegovy and Mounjaro?
Both are prescription weight loss injections licensed in the UK. Wegovy (semaglutide) is a GLP-1 agonist; Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist with a slightly different mechanism. Clinical trials show similar average weight loss (15–21%). Both are once-weekly injections. Your prescriber will advise which suits your situation best. Individual results vary.
Can I get weight loss injections on the NHS?
Yes, but access is through specialist tier 3 weight management services, not standard GP prescription. You'll need a GP referral and may face waiting lists. Availability varies by region (ICB). Private prescribing offers faster access without NHS referral, though costs apply.
Are weight loss injections safe?
Prescription weight loss injections are licensed and regulated in the UK. They require clinical assessment before use. Common side effects include nausea and gastrointestinal changes. Serious side effects are rare but can occur. Always discuss full risks and suitability with your prescriber before starting.
How much weight will I lose?
Clinical trials show average weight loss of around 15–21% of body weight over several months, though individual results vary significantly. Some people lose more, some less. Weight loss depends on dose, adherence, diet, exercise, genetics, and medical factors. Your prescriber cannot assures specific outcomes.
Do I need a prescription from my GP?
If accessing through NHS specialist services, yes — your GP refers you. For private prescribing, you consult directly with a UK-licensed prescriber (no GP referral needed). Either way, a prescription from a qualified healthcare professional is required before any weight loss injection can be dispensed.
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.