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 Products: UK Prescription Options
If you're looking for weight loss products in the UK, prescription medications are now available for eligible adults. Unlike over-the-counter supplements, prescription weight management options like Mounjaro and Wegovy are evidence-based treatments that work alongside diet and exercise. This guide explains what's available on the NHS and privately, who qualifies, and how to find out if prescription weight loss medication might be right for you.
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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.
UK-Licensed Prescription Weight Loss Products
Three prescription weight loss medications are currently licensed in the UK for weight management in adults. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — meaning it activates two natural hormone pathways that help regulate appetite and support feeling fuller after meals. Wegovy (semaglutide) is a GLP-1 receptor agonist available as once-weekly injections, with clinical trials showing average weight loss of around 15% of body weight. Saxenda (liraglutide) is an older GLP-1 option requiring daily injections rather than weekly.
All three are prescription-only and require a clinical assessment before being prescribed. In clinical trials, these medications worked best when combined with a reduced-calorie diet and increased physical activity. Individual results vary significantly — some people lose more weight than others at the same dose.
- Mounjaro doses: 2.5 mg to 15 mg weekly
- Wegovy doses: 0.25 mg to 2.4 mg weekly
- Saxenda doses: 0.6 mg to 3 mg daily
Use our free GLP-1 weight loss calculator above to explore potential weight loss at different doses.
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 Access vs Private Prescription Routes
In the UK, you can access prescription weight loss medication through two routes. NHS access is through specialist tier 3 weight management services — you'll need a referral from your GP, and availability varies significantly by region. NHS waiting lists can be lengthy, sometimes months or years depending on where you live. Private access is available through online consultations with UK-licensed prescribers; if eligible, a prescription is issued and dispensed by a registered pharmacy.
Eligibility generally requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. For adults of South Asian, Black African, or Black Caribbean heritage, lower BMI thresholds apply due to higher health risk at lower weights. Start the conversation with your GP — they can advise on NHS options and what's suitable for your individual health profile.
- 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 Mounjaro and Wegovy?
Mounjaro activates two hormone pathways (GIP and GLP-1), while Wegovy activates one (GLP-1 only). Clinical trials suggest Mounjaro may result in slightly higher average weight loss, but individual results vary. Both are once-weekly injections. Only a prescriber can determine which is right for you.
Can I get prescription weight loss medication on the NHS?
Yes, but access is through specialist weight management services, not standard GP prescriptions. You'll need a referral from your GP to tier 3 services. Availability and waiting times vary significantly by region and ICB (integrated care board).
How do I know if I'm eligible for prescription weight loss products?
Generally, you need a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea. For certain ethnic groups, lower BMI thresholds apply. Your GP or a licensed prescriber can assess your individual eligibility.
Are there side effects with prescription weight loss medications?
Yes. Common side effects include nausea, diarrhoea, vomiting, and constipation — usually temporary. Serious side effects are rare but possible. Your prescriber will discuss all risks and benefits with you before prescribing.
How quickly do prescription weight loss products work?
Most people see gradual weight loss over weeks and months, not overnight. The NHS recommends healthy weight loss of 0.5–1 kg per week. Prescription medications work best alongside a reduced-calorie diet and increased physical activity — they're not a replacement for lifestyle changes.
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.