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
Free tracker included with every download this week
Water with Lemon for Weight Loss — What the Evidence Shows
Water with lemon is often promoted for weight loss, but there's no scientific evidence it causes fat loss on its own. While staying hydrated is important for overall health and may support weight management efforts, sustainable weight loss in the UK typically requires either lifestyle changes (diet and exercise) or prescription medication for eligible adults. If you're looking to lose weight, your GP can discuss options suited to your individual circumstances, including registered prescription treatments now available through the NHS and private healthcare.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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 Management Options
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), you may be eligible for prescription weight loss medication in the UK. Three medicines are currently licensed for weight management:
- Mounjaro (tirzepatide) — once-weekly injection, dual GIP and GLP-1 receptor agonist; clinical trials showed average weight loss of 15–21% body weight
- Wegovy (semaglutide) — once-weekly injection, GLP-1 receptor agonist; average weight loss approximately 15% in clinical trials
- Saxenda (liraglutide) — daily injection, GLP-1 receptor agonist
These are prescription-only medicines and work alongside reduced-calorie diet and increased physical activity — not as replacements for lifestyle changes. Individual results vary significantly. You can use our free GLP-1 weight loss calculator to explore potential outcomes at different doses, and our BMI calculator to check your current classification.
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 and Next Steps
In the UK, prescription weight loss medication is available through two routes. NHS access is through specialist tier 3/4 weight management services — ask your GP for a referral, though waiting lists vary significantly by region. Private access is through GPhC-registered online pharmacies following a clinical assessment with a UK-licensed prescriber, available without NHS referral. To find out if you qualify, calculate your BMI using the free converter on this page, then speak with your GP or complete an online assessment with a private prescriber. Both routes require a clinical evaluation to confirm suitability based on your health history, medications, and individual circumstances.
- 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.
Does drinking water with lemon actually help you lose weight?
Water with lemon has no proven fat-loss properties. Staying hydrated supports metabolism and may reduce thirst-driven eating, but weight loss requires a calorie deficit. Lemon adds negligible calories and nutrients but isn't a weight loss treatment. Prescription medication, combined with dietary changes and exercise, is evidence-based for significant weight loss in eligible adults.
What qualifies me for prescription weight loss medication in the UK?
You may qualify if you have a BMI of 30 or above, or BMI of 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, heart disease, or sleep apnoea). Lower thresholds apply for South Asian, Chinese, Black African, and Black Caribbean adults. Your GP or a licensed prescriber can assess your eligibility based on your individual health profile.
How much weight can I expect to lose with Mounjaro or Wegovy?
Clinical trials showed average weight loss of 15–21% body weight with Mounjaro and approximately 15% with Wegovy over 68–72 weeks, alongside a reduced-calorie diet and exercise. Individual results vary significantly — some people lose more, some less. Weight loss is not assured, and results depend on adherence, lifestyle changes, and individual metabolism.
Is prescription weight loss medication available on the NHS?
Yes. Mounjaro and Wegovy are approved for NHS use in specialist weight management services. However, NHS availability varies by region, and waiting lists can be lengthy. Private prescription is also available through GPhC-registered pharmacies following online clinical assessment. Ask your GP about NHS referral options in your area.
Can I get weight loss injections without seeing my GP?
Yes, through private online prescribing. A UK-licensed prescriber conducts a clinical assessment, and if suitable, issues a prescription to a GPhC-registered pharmacy. However, your GP should be informed of any medication you take. NHS access requires a GP referral to specialist services. Either route involves clinical evaluation — these are prescription-only medicines, not over-the-counter products.
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.