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 in UK Pharmacies — What You Need to Know
Weight loss injections are prescription-only medicines available in the UK through NHS specialist services or regulated private pharmacies. These GLP-1 and GLP-1/GIP medications may help with weight management when used alongside lifestyle changes. Access depends on eligibility criteria and clinical assessment. This guide explains how weight loss injections work, who can access them, the different options available, and what to expect when getting started. Individual results vary, and a prescription from a UK-licensed prescriber is always required.
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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.
Understanding Weight Loss Injections and Pharmacy Access
Weight loss injections are prescription-only medicines that work by activating natural hormone pathways in the body. The two main UK-licensed options are Wegovy (semaglutide), a once-weekly GLP-1 injection, and Mounjaro (tirzepatide), a once-weekly dual GIP/GLP-1 injection. Both medications may help reduce appetite and support feeling fuller after smaller meals. Clinical trials showed these medications helped participants lose an average of 15–21% of their body weight alongside reduced-calorie diet and increased physical activity — though results vary significantly between individuals.
Pharmacy access in the UK works differently depending on whether you go through the NHS or private route. NHS specialist weight management services can prescribe these medications, though availability varies by region and waiting lists can be lengthy. Alternatively, GPhC-registered private online pharmacies can dispense weight loss injections following an online clinical assessment with a UK-licensed prescriber. Both pathways require a valid prescription — weight loss injections are never available over-the-counter or without clinical assessment.
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 Getting a Prescription
To access prescription weight loss injections in the UK, you must meet specific eligibility criteria. Adults with a BMI of 30 kg/m² or above (obesity), or a BMI of 27–29.9 (overweight) with at least one weight-related health condition, may qualify. Weight-related conditions include type 2 diabetes, prediabetes, high blood pressure, abnormal blood fats, obstructive sleep apnoea, or history of heart attack or stroke.
For adults of South Asian, Chinese, Black African, or Black Caribbean heritage, lower BMI thresholds apply — eligibility may start at BMI 27.5 or above due to higher health risks at lower weights. Use our free BMI calculator above to check your personal BMI instantly. A prescriber will then assess whether weight loss injection treatment is appropriate for you based on your individual health profile, medications, and medical history.
NHS access: Request a referral from your GP to a tier 3 or tier 4 specialist weight management service. These services offer comprehensive support including dietary advice and behavioural coaching. Availability and waiting times vary significantly by NHS region.
Private pharmacy access: Complete an online consultation with a UK-licensed prescriber. If approved, your prescription is dispensed by a GPhC-registered pharmacy. Private costs typically range from £129–£320 per month depending on medication and dose. You can track your progress using our free progress tracker to monitor weight changes over time. Both routes require commitment to lifestyle changes — injections work best alongside healthy eating and physical activity.
- 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 without a prescription in the UK?
No. Weight loss injections are prescription-only medicines in the UK. They require an assessment and prescription from a UK-licensed prescriber — either through NHS specialist services or private online prescribers. They are never available over-the-counter or without clinical evaluation.
What's the difference between Wegovy and Mounjaro?
Wegovy (semaglutide) is a GLP-1 injection taken once weekly. Mounjaro (tirzepatide) is a dual GIP/GLP-1 injection, also once weekly. Both may support weight loss, but Mounjaro uses a different mechanism with two hormone pathways. Clinical trials showed comparable results, though individual responses vary. Your prescriber will discuss which is suitable for you.
How much do weight loss injections cost on the NHS?
Weight loss injections are available on the NHS through specialist weight management services, though eligibility and availability vary by region. If prescribed, you pay only standard NHS prescription charges (currently £9.90 per item in England). Private costs range from £129–£320 monthly depending on dose and provider.
How long do I need to take weight loss injections?
This depends on your individual health and goals. Some people continue treatment long-term; others use it to reach a target weight then transition to maintaining that weight through lifestyle changes alone. Your prescriber will discuss the right timeline for you and monitor your progress regularly.
Can I use our BMI calculator to check my eligibility for weight loss injections?
Yes. Our free BMI calculator helps you understand your current BMI category. However, eligibility for weight loss injections also depends on weight-related health conditions and individual assessment. Use the calculator as a starting point, then discuss eligibility with your GP or a prescriber who can evaluate your full health profile.
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.