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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Weight Loss Injections Online in the UK — What You Need to Know
Weight loss injections are now available online in the UK through licensed prescribers, but they're prescription-only medications that require a clinical assessment. The most commonly discussed weight loss injections include Wegovy (semaglutide) and Mounjaro (tirzepatide)—both GLP-1 or dual-action medications approved for weight management. This guide explains how these injections work, who can access them, and what the prescription process involves. Always consult your GP before considering any weight management medication, especially if you have existing health conditions.
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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
Weight loss injections like Wegovy and Mounjaro are GLP-1 receptor agonist medications that mimic natural hormones produced in your gut. They work by:
- Reducing appetite and food cravings
- Helping you feel fuller after smaller meals
- Slowing how quickly food leaves your stomach
- Supporting better blood sugar regulation
In clinical trials (the STEP studies), Wegovy helped participants lose an average of around 15% of their body weight when used alongside a reduced-calorie diet and increased physical activity. Mounjaro, a dual GIP and GLP-1 agonist, showed average weight loss of 15–21% in clinical trials. However, individual results vary significantly—some people lose more, some less. These are not effective injections; they work best as part of a comprehensive weight management approach that includes dietary changes and lifestyle modifications.
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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.
How to Access Weight Loss Injections in the UK
In the UK, weight loss injections are prescription-only and can be accessed through two main routes: NHS specialist services and private prescribing. On the NHS, you typically need referral to a tier 3 specialist weight management service, though availability varies significantly by region and waiting lists can be lengthy. Privately, licensed prescribers can issue prescriptions following an online clinical assessment, dispensed by GPhC-registered pharmacies. Eligibility generally requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure. Use our free BMI calculator to check your personal BMI, and discuss options with your GP before pursuing private prescribing.
- 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.
Are weight loss injections available through a UK pharmacy online?
a UK pharmacy is a major UK pharmacy but does not provide weight loss injections through an online prescribing service of its own. Weight loss injections like Wegovy and Mounjaro are available through licensed online prescribers and dispensed by GPhC-registered pharmacies, but you'll need to access a dedicated weight loss service rather than a high street pharmacy.
Do weight loss injections require a prescription?
Yes, all weight loss injections including Wegovy and Mounjaro are prescription-only medications in the UK. They cannot be purchased over the counter. You must have a clinical assessment by a licensed prescriber (either NHS or private) to determine if they're suitable for your health profile.
What's the difference between Wegovy and Mounjaro?
Both are injectable weight management medications, but they work slightly differently. Wegovy (semaglutide) is a GLP-1 agonist with an average weight loss of around 15% in trials. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist with average weight loss of 15–21%. Mounjaro starts at lower doses and is injected once weekly, like Wegovy. Your prescriber will assess which suits your circumstances.
Can I get weight loss injections on the NHS?
Yes, weight loss injections are available on the NHS through specialist tier 3 weight management services, but access varies by region and typically involves a GP referral. NHS availability can involve waiting lists. Private prescribing offers faster access but involves costs. Check with your GP about NHS options in your area first.
How much do weight loss injections cost privately?
Private costs vary by provider and dose, typically ranging from approximately £129 to £320 per month depending on the medication and dose strength. NHS access is free, but involves referral and potential waiting times. Compare options with your GP and research licensed providers before committing.
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.