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 Buy Weight Loss Injection in the UK
Weight loss injections are prescription-only medications available in the UK through NHS specialist services or private online prescribing. The most commonly prescribed options are Wegovy (semaglutide) and Mounjaro (tirzepatide), both once-weekly GLP-1 receptor agonists that may help reduce appetite and support sustainable weight loss. Access depends on your eligibility, which is assessed based on BMI and weight-related health conditions. This guide explains how to obtain weight loss injections, what to expect, and how they work alongside lifestyle changes for weight management 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.
How Weight Loss Injections Work and Eligibility
Weight loss injections like Wegovy (semaglutide) are GLP-1 receptor agonists that mimic a natural hormone your gut produces after eating. They may help you feel fuller after smaller meals, reduce food cravings, and slow how quickly food leaves your stomach. In clinical trials, semaglutide helped people lose an average of around 15% of their body weight over 68 weeks, though individual results vary significantly.
UK eligibility typically requires:
- BMI of 30 kg/m² or above, or
- BMI of 27–29.9 kg/m² with a weight-related health condition (type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease)
- For South Asian, Chinese, Black African, or Black Caribbean adults: lower BMI thresholds often apply (27.5+)
You must also be 18 or over, not pregnant, and not breastfeeding. A prescriber will assess whether weight loss medication is clinically appropriate for you based on your individual health.
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 Access — How to Buy Weight Loss Injections
NHS Access: Available through tier 3 specialist weight management services by GP referral. Availability varies significantly by region, and waiting lists can be lengthy in many areas. Once prescribed, injections are dispensed through NHS pharmacy.
Private Access: Available through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber. No NHS referral needed. Costs typically range from £129–£320 per month depending on dose. Prescriptions are issued if clinically appropriate following your assessment. Private prescribers assess eligibility using the same clinical criteria as NHS services. Try our free BMI calculator above to check if you may meet the eligibility threshold, or use our GLP-1 weight loss calculator to estimate potential results at different doses.
- 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.
Is weight loss injection the same as Ozempic?
No. Ozempic and Wegovy both contain semaglutide, but Ozempic is approved for type 2 diabetes (not weight loss) and uses lower doses. Wegovy is the licensed weight management version in the UK with doses up to 2.4 mg specifically for weight loss. Using Ozempic for weight loss off-label is not recommended.
Can I get weight loss injections without a prescription?
No. Weight loss injections including Wegovy and Mounjaro are prescription-only medicines in the UK. You must be assessed and prescribed by a licensed healthcare professional — either through NHS specialist services or a private online prescriber — before obtaining the medication.
How long does weight loss injection take to work?
Most people notice appetite reduction within the first few weeks of starting. However, meaningful weight loss typically takes 8–12 weeks to become noticeable. Clinical trials measured results over 68 weeks (approximately 16 months), so sustainable weight loss is a gradual process. Individual timescales vary.
Are weight loss injections used alone or with diet changes?
Weight loss injections are used alongside a reduced-calorie diet and increased physical activity — not instead of lifestyle changes. Clinical trial results were achieved when participants combined the injection with dietary modifications and exercise. Medication supports these efforts but doesn't replace them.
What happens if I stop using weight loss injection?
Weight loss effects typically plateau once you stop the injection. People may gradually regain some weight if lifestyle changes (diet and exercise) are not maintained long-term. Your prescriber can discuss a personalised plan including how long to use the medication and long-term weight management strategies.
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.