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 Medication Available in UK Pharmacies
If you're looking for prescription weight loss medication in the UK, several effective options are now available through both NHS specialist services and private pharmacies. Weight management in the UK has expanded significantly beyond diet and exercise alone, with licensed prescription medications offering evidence-based support for eligible adults. Understanding what's available, how to access it, and whether you qualify is the first step toward informed weight loss decisions. This guide covers the key prescription options, eligibility criteria, and pathways to obtain medication through UK pharmacies.
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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.
Prescription Weight Loss Medications Licensed in the UK
Three main prescription medications are licensed for weight management in the UK:
- Mounjaro (tirzepatide) — A once-weekly GIP and GLP-1 receptor agonist injection. Doses range from 2.5 mg to 15 mg weekly. Clinical trials showed participants lost an average of 15–21% of body weight alongside diet and exercise changes.
- Wegovy (semaglutide) — A once-weekly GLP-1 injection with doses up to 2.4 mg weekly. Evidence suggests average weight loss of around 15% of body weight over the trial period.
- Saxenda (liraglutide) — A daily GLP-1 injection at up to 3 mg. It has the longest track record of use for weight management globally.
All three are prescription-only medicines in the UK. Eligibility depends on BMI and health status. Use our free GLP-1 weight loss calculator to explore potential outcomes with different medication types, and our BMI calculator to check your current status.
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 — Finding Weight Loss Medication
NHS access: Prescription weight loss medication is available through specialist tier 3 or tier 4 weight management services. You'll need a GP referral, and availability varies significantly by region. Waiting lists can be lengthy in many areas, though this varies by NHS Integrated Care Board (ICB).
Private access: Weight loss medication is also available through GPhC-registered online pharmacies following an assessment with a UK-licensed prescriber. This route doesn't require NHS referral and is typically faster, though there is a cost. Speak with your GP first — they can advise whether medication is appropriate for you and may discuss both NHS and private pathways. A prescriber will assess your individual health, BMI, and weight-related conditions to determine suitability.
- 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 BMI do I need to be eligible for prescription weight loss medication?
Adults with a BMI of 30 kg/m² or above are typically eligible. You may also qualify with a BMI of 27–29.9 kg/m² if you have weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. For people of South Asian, Chinese, Black African, or Black Caribbean heritage, the NHS recommends lower thresholds due to higher health risk at lower BMI levels.
How do I get prescription weight loss medication through the NHS?
Ask your GP for a referral to your local tier 3 specialist weight management service. They will assess you and determine whether prescription medication is appropriate alongside lifestyle changes. Availability and waiting times vary by region. Check your local NHS Integrated Care Board website for information about services in your area.
Can I buy weight loss medication from a private pharmacy without NHS referral?
Yes. Private online pharmacies registered with the GPhC can dispense prescription weight loss medications following an assessment by a UK-licensed prescriber. This route is faster but involves a cost. Always ensure any prescriber and pharmacy are UK-registered and legitimate before proceeding.
What's the difference between Mounjaro and Wegovy for weight loss?
Both are once-weekly injections, but they work slightly differently. Mounjaro is a dual GIP and GLP-1 agonist with average weight loss of 15–21% in trials. Wegovy is a GLP-1 agonist alone with average weight loss around 15%. Individual results vary significantly. A prescriber can help determine which is more suitable for your circumstances.
Do weight loss medications work without diet and exercise changes?
No. Prescription weight medications like Mounjaro and Wegovy are most effective when combined with a reduced-calorie diet and increased physical activity. They support weight loss by reducing appetite and food cravings, but sustainable results require lifestyle changes. Track your progress with our free progress tracker and discuss dietary support with your GP or a dietitian.
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.