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 With Weight Loss?
Drinking water can support weight loss, but it's not a clinically supported solution on its own. Research shows that staying hydrated may help you feel fuller, reduce hunger signals, and support your metabolism slightly. However, sustainable weight management in the UK requires a calorie deficit alongside lifestyle changes. Our free BMI calculator can help you understand your current weight status, whilst our GLP-1 weight loss calculator shows how prescription weight loss medication might support your goals when combined with proper hydration and nutrition.
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
Water plays a supportive role in weight management through several mechanisms. Drinking water before meals may increase feelings of fullness, potentially reducing overall calorie intake. Research suggests that proper hydration helps your body's metabolic processes function efficiently. Additionally, staying hydrated supports kidney function during weight loss, which is important when your body is breaking down fat stores.
- Water has zero calories, making it an ideal alternative to sugary drinks and fizzy beverages
- Drinking water can help distinguish between genuine thirst and hunger — often what feels like hunger is actually dehydration
- Cold water may temporarily boost metabolic rate slightly, though the effect is modest
- Staying hydrated supports exercise performance and recovery, which aids weight loss efforts
However, water alone won't create the calorie deficit needed for weight loss. The NHS emphasises that sustainable weight loss requires a reduced-calorie diet alongside increased physical activity. Using our weight converter and BMI calculator can help you set realistic targets based on your current measurements.
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 considering prescription weight loss medication like GLP-1 injections, staying well hydrated becomes even more important. These medications can cause nausea and constipation, conditions where adequate water intake is essential. Patients taking weight loss injections alongside dietary changes experience better outcomes when they maintain consistent hydration and follow NHS weight management guidance.
Our GLP-1 weight loss calculator can help estimate potential results when medication is combined with proper nutrition and hydration. Remember, any weight loss medication requires a prescription from a licensed prescriber following a clinical assessment — it's never used as a substitute for lifestyle changes, but rather alongside them for maximum benefit.
- 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 around 6–8 glasses of water daily for general health. During weight loss, ensure you're drinking enough to stay hydrated, but there's no evidence that excessive water consumption (beyond normal thirst) accelerates weight loss. Individual needs vary based on activity level, climate, and metabolism.
Can drinking water replace a calorie deficit for weight loss?
No. Water supports weight loss but cannot replace a calorie deficit. To lose weight sustainably, you need to consume fewer calories than you burn. The NHS recommends losing 0.5–1 kg per week, which typically requires a deficit of around 500 kcal daily. Water helps manage hunger but isn't a substitute for dietary changes.
Does drinking water boost metabolism significantly?
Water has a modest effect on metabolism. Drinking cold water causes a temporary, small increase in calorie burn (around 4–8 calories per glass), but this effect is minimal compared to the impact of diet and exercise. It's a supportive factor, not a primary weight loss mechanism.
Is water better than other drinks for weight loss?
Yes, water is ideal for weight loss because it contains no calories, sugar, or artificial sweeteners. Sugary drinks, alcohol, and high-calorie beverages add unnecessary calories. If you find plain water boring, try adding lemon or herbal tea — just avoid adding sugars or sweeteners that would undermine your weight loss goals.
How does hydration help if I'm taking weight loss medication?
Staying hydrated is particularly important with prescription weight loss injections, as these medications can cause nausea, constipation, and other digestive effects. Adequate water intake helps manage these side effects and supports your body during the weight loss process. Always consult your prescriber about hydration during treatment.
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.