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
Does Water Aid Weight Loss?
Water alone does not directly cause weight loss, but staying hydrated plays an important supporting role in weight management and overall health. Drinking adequate water may help reduce hunger, support metabolism, and improve exercise performance — all factors that can contribute to a successful weight loss plan. Combined with a balanced diet and physical activity, proper hydration is part of an effective approach to reaching a healthier weight. If you're considering prescription weight loss medication through NHS weight loss services or private options, hydration remains an essential daily habit to support your progress.
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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.
How Water Supports Weight Management
Water plays several practical roles in weight management, though it is not a weight loss solution on its own:
- Appetite regulation: Drinking water before meals may help you feel fuller, potentially reducing overall calorie intake. The stomach responds to volume, and water takes up space without adding calories.
- Metabolism support: Some research suggests that drinking cold water temporarily increases metabolic rate as your body warms it — though the effect is modest (around 3–5% increase).
- Exercise performance: Proper hydration improves physical performance and endurance, enabling more effective exercise sessions, which supports weight loss when combined with calorie reduction.
- Reducing liquid calories: Replacing sugary drinks, alcohol, and high-calorie beverages with water eliminates hundreds of calories per week — a proven weight loss strategy.
The NHS recommends drinking 6–8 glasses (about 1.5 litres) of fluids daily for adults, though individual needs vary based on activity level and climate.
Clinically BackedWeight Loss
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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.
Water and Weight Loss Medication
If you're exploring prescription weight loss medication like GLP-1 weight loss injections (Mounjaro or Wegovy), staying hydrated becomes even more important. These medications may cause nausea, constipation, and other digestive side effects — adequate water intake helps manage these symptoms. Additionally, when losing weight more rapidly with medication support, maintaining proper hydration supports metabolic health and reduces risk of muscle loss. Calculate your potential weight loss progress using our GLP-1 weight loss calculator, and track your results alongside consistent hydration habits. Always follow your prescriber's guidance on fluid intake, especially if you experience side effects affecting digestion.
- 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.
How much water should I drink daily for weight loss?
The NHS recommends 6–8 glasses (approximately 1.5 litres) of fluid daily for most adults. During exercise or in hot weather, you may need more. Thirst is a reliable indicator — drink when you feel thirsty. There is no single "ideal" amount for weight loss; consistent hydration matters more than a specific volume.
Does drinking water before meals help with weight loss?
Drinking water (or eating water-rich foods like soups) before meals may help you feel fuller and eat fewer calories overall. Some studies show modest benefits, but this works best when combined with balanced nutrition and calorie awareness. It is one small tool in a broader weight management strategy, not a standalone solution.
Can water alone cause weight loss?
No. Water has no calories and does not directly burn fat. Weight loss requires a calorie deficit — consuming fewer calories than you burn. Water supports this by reducing hunger and replacing calorie-dense drinks, but diet and activity level are the primary drivers of weight loss.
Does drinking cold water boost metabolism?
Drinking cold water does temporarily increase metabolic rate as your body warms it, but the effect is very small — approximately 3–5% for a short period. This is not a significant weight loss mechanism on its own, though every small positive habit contributes to overall health.
Is water intake important with weight loss medication like Mounjaro or Wegovy?
Yes. GLP-1 medications may cause nausea, constipation, and other digestive effects. Adequate hydration helps manage these side effects and supports overall health during weight loss. Always discuss fluid intake with your prescriber if you experience digestive symptoms.
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.