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 Drinking Lots of Water Help Weight Loss?
Yes, drinking more water can support weight loss, but it's not a clinically supported solution on its own. Water helps you feel fuller, may slightly boost metabolism, and can reduce thirst-driven eating. However, sustainable weight loss requires a calorie deficit alongside physical activity. If you're considering nhs weight loss support or exploring prescription weight loss uk options, hydration is one part of a complete weight management uk approach—not a replacement for dietary changes or, where appropriate, medical intervention.
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.
How Water Supports Weight Loss
Drinking water helps weight loss in several practical ways. First, water fills your stomach, which can make you feel fuller before and during meals—meaning you may eat smaller portions naturally. Second, your body burns calories digesting water (though the effect is modest). Third, thirst is often mistaken for hunger—drinking water prevents unnecessary snacking. Studies show people who drink water before meals consume fewer calories overall.
- Drinking 500ml of water before meals may reduce calorie intake by up to 13%
- Staying hydrated improves exercise performance, helping you move more
- Water has zero calories, unlike sugary drinks which add excess energy intake
- Proper hydration supports metabolism and fat burning
However, water alone won't create the calorie deficit needed for weight loss. You still need to eat fewer calories than you burn. This is why nhs weight loss programmes always combine hydration advice with dietary changes and physical activity.
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.
Water and Weight Loss Medication
If you're exploring glp-1 weight loss options like Mounjaro or Wegovy, staying hydrated becomes even more important. These prescription weight loss uk medications can cause nausea, constipation, and diarrhoea—all reasons to drink plenty of water. Use our free BMI calculator above to check if prescription weight loss medication might be suitable for you, then discuss hydration and lifestyle changes with your GP. Remember that medication works best alongside a reduced-calorie diet and regular physical activity, not instead of them.
- Water intake supports medication tolerability
- Dehydration can worsen side effects of weight loss injections
- Combine hydration with dietary changes for best results
- 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 to 8 glasses (about 1.5 litres) of water per day for general health. For weight loss, drinking this amount—plus extra water before meals—supports your efforts. However, individual needs vary based on activity level and climate. Your GP can advise on your personal needs.
Does drinking water speed up metabolism?
Drinking water does increase energy expenditure slightly (thermogenesis), but the effect is modest—roughly 100 calories per day extra. Water's main weight loss benefit is appetite suppression and preventing sugar-sweetened drink consumption, not metabolic acceleration.
Can water alone help me lose weight?
No. Water supports weight loss but cannot create the calorie deficit needed on its own. You must also reduce calorie intake and increase physical activity. Use our free GLP-1 weight loss calculator to explore all options available for weight management uk.
Is drinking water important if I'm taking weight loss medication?
Yes. Medications like Mounjaro and Wegovy can cause dehydration, nausea, and constipation. Staying well-hydrated helps manage these side effects and supports the medication's effectiveness. Always follow your prescriber's guidance.
What's the best time to drink water for weight loss?
Drinking 500ml of water about 30 minutes before meals is particularly effective—it fills your stomach and reduces calorie intake at that meal. However, sipping water throughout the day is equally important for hydration and appetite control.
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.