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 Drinks and UK Prescription Medication
Homemade weight loss drinks can support hydration and healthy habits, but prescription medication may be more effective for significant weight management in the UK. This guide covers both natural approaches and UK-licensed prescription options including Mounjaro and Wegovy, available through NHS specialist services or private prescribing. Learn which option might suit your situation and how to discuss weight management with your GP.
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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
For adults looking for medically-supported weight management in the UK, three prescription-only medications are currently licensed:
- Mounjaro (tirzepatide) — once-weekly injection; dual GIP and GLP-1 receptor agonist; average weight loss ~15–21% body weight in clinical trials
- Wegovy (semaglutide) — once-weekly injection; GLP-1 receptor agonist; average weight loss ~15% body weight
- Saxenda (liraglutide) — daily injection; GLP-1 receptor agonist; slightly lower average weight loss than Mounjaro or Wegovy
These are prescription-only medicines requiring a clinical assessment before prescription. They work by helping regulate appetite and food cravings, and are prescribed alongside dietary changes and increased physical activity — not as a replacement for lifestyle adjustments.
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 Prescribing in the UK
NHS weight loss medication is available through tier 3 specialist weight management services, typically accessed via GP referral. Eligibility generally requires a BMI of 30 or above, or 27 or above with weight-related health conditions such as type 2 diabetes or high blood pressure. However, NHS waiting lists can be very long in many regions. Private prescribing is available through GPhC-registered online pharmacies following a remote clinical assessment — no NHS referral required. Your GP can help you understand eligibility and discuss which option might be appropriate for you.
- 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.
Can homemade weight loss drinks replace prescription medication?
Homemade drinks can support hydration and healthy habits, but prescription medications like Mounjaro or Wegovy are clinically proven to produce significant weight loss when combined with diet and exercise. Drinks alone are unlikely to achieve major weight loss. A combination of lifestyle changes and, if eligible, prescription support often works best.
Who is eligible for weight loss medication in the UK?
Generally, adults with a BMI of 30 or above, or 25–29.9 with weight-related conditions like type 2 diabetes, high blood pressure, or sleep apnoea may be eligible. Eligibility is assessed individually by a prescriber. South Asian, Chinese, and Black African/Caribbean adults may qualify at lower BMI thresholds due to higher health risks at those levels.
What is the difference between Mounjaro and Wegovy?
Both are once-weekly injections, but Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), whilst Wegovy (semaglutide) activates one (GLP-1). In clinical trials, Mounjaro showed slightly higher average weight loss (~20.9%) compared to Wegovy (~14.9%), though individual results vary significantly.
How do I access weight loss medication through the NHS?
Ask your GP for a referral to your local specialist weight management service (tier 3). They will assess your eligibility, medical history, and suitability. NHS availability varies by region and waiting times can be substantial. Private prescribing is an alternative if you want faster access following an online clinical assessment.
Are weight loss injections like Mounjaro suitable for everyone?
No. Prescription weight loss medications are not suitable for pregnant or breastfeeding individuals, people under 18, those with certain medical conditions, or those allergic to the active ingredients. A clinical assessment by a prescriber is essential to determine suitability. Always discuss your full medical history with your GP or prescriber.
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.