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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Dietary Supplements and Weight Loss Medication in the UK
While many dietary supplements claim to support weight loss, prescription weight management options available in the UK offer clinically proven results. For adults struggling with excess weight, understanding both supplement alternatives and licensed prescription medications — such as Mounjaro, Wegovy, and Saxenda — can help you make an informed decision about the most suitable approach for your health goals. This guide covers NHS weight loss medication options, eligibility criteria, and how to explore what's available to you.
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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.
UK-Licensed Prescription Weight Loss Options
Three prescription medications are currently licensed in the UK for weight management:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist, once-weekly injection, doses from 2.5 mg to 15 mg. Clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks.
- Wegovy (semaglutide) — a GLP-1 receptor agonist, once-weekly injection, maximum dose 2.4 mg. STEP trials demonstrated average weight loss of approximately 15% at the highest dose.
- Saxenda (liraglutide) — a GLP-1 receptor agonist, daily injection, maximum 3 mg per day. Typically produces slightly lower average weight loss than weekly options.
All three are prescription-only medicines requiring a clinical assessment before prescription. Individual results vary significantly. These medications work best when combined with reduced-calorie diet and increased physical activity. Use our free GLP-1 weight loss calculator to explore potential outcomes 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 and Private Options for Weight Loss Medication
NHS route: Prescription weight loss medication is available through NHS specialist tier 3 weight management services, typically requiring a GP referral. Access varies significantly by region and availability can be limited, with waiting lists in some areas extending many months. Your GP can assess your eligibility and refer you if appropriate.
Private route: GLP-1 weight loss medications are available through GPhC-registered online pharmacies following a clinical consultation with a UK-licensed prescriber. This route bypasses NHS waiting lists but involves private costs, typically ranging from £129–£320 per month depending on dose.
Eligibility: Adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, sleep apnoea) may qualify. For South Asian, Chinese, Black African, or Black Caribbean adults, lower BMI thresholds apply. Calculate your BMI using our free BMI calculator to assess where you stand.
- 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 dietary supplements and prescription weight loss medication?
Dietary supplements are unregulated food products with limited clinical evidence. Prescription weight loss medications like Mounjaro and Wegovy are licensed medicines with rigorous clinical trial data showing average weight loss of 15–21%. Prescription options require medical assessment and ongoing GP monitoring; supplements do not. For significant weight loss support, prescription medication offers stronger clinical backing.
Am I eligible for NHS weight loss medication?
Generally, yes, if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions like type 2 diabetes or high blood pressure. Lower BMI thresholds apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Speak to your GP for a personalised assessment and potential referral to specialist weight management services.
How quickly can I access prescription weight loss medication?
NHS access depends on your region and specialist service availability — waiting lists can range from weeks to many months. Private online prescribing is typically faster, often within days. Both routes require a clinical assessment. Your GP can advise on NHS timelines in your area.
Do prescription weight loss injections work without diet and exercise changes?
No. Clinical trials showed weight loss medication works best alongside a reduced-calorie diet and increased physical activity. These medications support appetite control and fullness, but sustainable weight loss requires lifestyle changes. NHS guidance emphasises combining medication with behaviour modification for best results.
What's the cost of prescription weight loss medication in the UK?
On the NHS, there is no patient cost beyond standard prescription charges (currently £9.65 per item in England). Private prescriptions range from approximately £129–£320 per month depending on medication, dose, and provider. Some private providers offer subscription models or bulk-purchase discounts.
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.