You’ve probably heard the classic “eight glasses a day” guideline for how much water we should drink. As with most health-related advice, though, it’s not always that simple.
We know that we need a certain amount of protein, fat, and carbohydrates daily, and you might even track your calories or macros. But most people don’t know exactly how much water they need, let alone keep track of their fluid intake. And that’s a big mistake!
As a nutritionist and exercise scientist, I’ve seen first-hand the impacts of dehydration. Most clients I work with just don’t get enough fluids for their bodies to thrive, even when they’re exercising regularly.
Think of it this way: if I told you there was a new product on the market that helps optimise your metabolism, improve your energy levels, boost your immune system and protect you against chronic illness, how many people would pull out their wallets immediately?
Oh, and here’s the best part: it’s already available to you for free. Crazy, right? But in reality, most of us still don’t drink enough water each day.
So, let’s dive into the facts and myths about how much water your body needs. I’ll unpack:
- How to calculate your ideal water intake
- Why drinking enough water is so critical
- Signs you need to drink more fluids
- Four sneaky causes of dehydration
and many more common questions about staying hydrated.
By the end of this article, you’ll have a clearer understanding of how much water you should be drinking – and why it matters!
How Much Water Should I Drink a Day?
A general guideline is to aim for at least 8 glasses of water per day, or 30ml per kilogram of body weight. To calculate how much water you need to drink, multiply your weight in kilos by 30, then divide by 1000 – that’s how many litres of water to aim for.
Eight glasses a day is the classic recommendation, but as you might have realised when clothes shopping, ‘one size fits all’ doesn’t really work for anyone! How much water you need varies from person to person, and even day to day, based on factors like:
- Age: As we get older, our ‘thirst signals’ are less reliable, so older adults will need to consciously drink more water.
- Activity level: The more active you are, the more water you’ll lose through sweat and the more you’ll need to top up.
- Climate and weather: You’ll need to drink more as the weather warms up, especially if you live in a hotter-than-average region.
- Pregnancy/breastfeeding: When pregnant or breastfeeding, you’re drinking for two – so be sure to stay properly hydrated.
- Health conditions: Some medical conditions, like kidney disease or diabetes, affect your ideal water intake (as do certain medications that speed up fluid loss).
- Alcohol & caffeine intake: Make extra effort to hydrate if you’re drinking alcohol (especially in hot weather) or lots of tea and coffee since these are diuretics.
Note: If you have a medical condition, ask your health practitioner about how much water you should be drinking. More isn’t always better – for example, if your kidneys are compromised, you’ll want to get the ‘all clear’ to add water or electrolytes to your diet.
With higher amounts of water, you may need additional salt or electrolytes to maintain a healthy balance, especially if you’re losing fluids through heavy sweating or illness.
Learn More: Hydration for Exercise & Sports: An Exercise Scientist’s Guide
Why is Hydration Important?
Our bodies are composed of about 75% water – it’s vital to regulate our temperature, remove waste, and transport nutrients where they’re needed. Water is so essential, it’s hard to list any bodily functions that don’t rely on being hydrated.
If we’re not drinking enough water, dehydration sets in, and the body can’t function normally. As we lose fluids, our vital organs get priority, leaving the rest of the body high and dry. Over time, even mild dehydration over time takes a toll on our health.
Neglecting to drink enough fluids leaves us vulnerable to a whole range of illnesses. Unfortunately, hydration is often overlooked, even when we’re trying to manage chronic health conditions.
Consider the last time you saw a doctor: did anyone ask you how much water you’re drinking? What about intense exercise and fluid loss? Were you asked about your consumption of coffee, alcohol or diuretic herbs?
If not, that’s a real oversight! Getting enough fluids in your diet helps your body function at its best, including fighting off illness or managing a chronic illness.
Drinking water proactively also has a ton of perks for our overall well-being – read all about them below!
10 Health Benefits of Staying Hydrated
Need some motivation to drink more water? Here are ten benefits of proper hydration for your body:
1. Boosts Energy Levels
Dehydration is a common cause of fatigue and low energy levels. Water is essential for the body to metabolise energy from food, as well as delivering nutrients and oxygen to the cells that need it. By staying hydrated, we can improve our energy levels and stay more alert throughout the day.
2. Improves Mood & Focus
Even mild dehydration can affect our mood, emotional regulation and focus. Drinking enough water can help improve our mental clarity, making it easier to stay calm and positive throughout the day.
3. Optimal Exercise Performance
Water is crucial for maximum athletic performance, and even mild dehydration can impact your workout. Staying hydrated helps maintain a healthy body temperature during exercise, decreasing fatigue and boosting endurance.
4. Aids in Weight Loss
Drinking water can support your weight loss goals in several ways. Firstly, it has zero calories and can help you feel full, which is handy to avoid overeating. Staying hydrated also supports your digestive health and keeps your metabolism working efficiently.
5. Reduces & Eases Headaches
Dehydration is a common cause of headaches and migraines. Keeping on top of your water intake is a natural way to reduce their frequency and severity. Preventing headaches is far better than treating them after the fact, and avoids the need to take painkillers.
6. Better Digestion
We often talk about the importance of gut health, but how often is fluid intake mentioned as a factor? Drinking enough water helps the body break down and digest food, and of course, it keeps everything moving smoothly, preventing constipation.
7. Strong Immune System
Water plays a vital role in maintaining immune system function. It’s essential to the production of lymph, which carries immune cells throughout the body, ready to fight off any invading nasties.
8. Detoxifies the Body
You may think of ‘a detox’ as a short-term diet program, but our bodies are naturally flushing out toxins all the time. Water is essential to detoxify the body, supporting healthy liver and kidney function.
9. Helps to Prevent Kidney Stones
Drinking enough water each day helps dissolve minerals and salts that can crystallise into kidney stones, reducing your risk. Staying well-hydrated also helps flush out small existing stones before they can get bigger.
10. Reduces Risk of UTIs
Urinary tract infections (UTIs) affect 50% of women in their lifetime, and many people struggle with them chronically. One of the best ways to avoid them is to drink enough fluids, helping to flush out UTI-causing bacteria.
Do I Need to Drink Water if I’m Not Thirsty?
Don’t wait until you’re parched to drink water! You’ve probably heard this before, but it’s true: by the time we feel thirsty, we’re usually in the early stages of dehydration.As adults, our thirst mechanisms aren’t very efficient, and they’re even less reliable as we age.
We can rely on our hunger cues to tell us when to eat, but we shouldn’t do the same with our water intake. If we wait a too long to eat, the body can still draw energy from fat to meet our caloric needs, but there’s no ‘backup source’ for staying hydrated.
If you’re only drinking when you’re thirsty, you’re playing catch up rather than staying on top of your body’s fluid needs. Chronic dehydration can cause fatigue, headaches, constipation, and even more serious issues like kidney stones and urinary tract infections. Yikes!
Can I Drink Too Much Water?
It is possible to drink too much water, but it isn’t a common issue. In some cases, like after endurance exercise, excessive water intake can lead to hyponatremia, where the sodium content of the blood is dangerously diluted.
More generally, the body can only absorb so much water at once, so spacing our your water intake is better than guzzling it all at once. If you’re losing minerals as well as fluids – like through intense exercise or gastro illness – be sure you replenish your electrolytes as well as fluids.
How Can I Tell if I’m Dehydrated?
Signs and symptoms of dehydration include:
- Dry mouth and lips
- Fatigue
- Irritability
- Headache
- Dizziness
- Dark-coloured urine (usually dark yellow or amber)
The tricky thing about dehydration is that you can’t always tell it’s starting until it’s too late.
Checking the colour of your urine is the best way to tell if you’re hydrated enough. A clear, light yellow is the goal – if it’s the colour of apple juice (or darker), you’re not getting enough fluids. Be sure to look at your urine colour during flow, not in the toilet bowl, since the toilet water will dilute it.
This urine colour chart is a great reference point:
Some common causes of dehydration include excessive sweating, diarrhoea, vomiting, and increased urination (caused by some medications and medical conditions). If you know you’re losing fluids, rehydration should be a priority to avoid more serious health complications.
4 Sneaky Causes of Dehydration
If we aren’t paying attention, it’s all too easy for dehydration to sneak up on us. There are so many factors that can increase our fluid loss, and if we aren’t careful, we might only realise once we’re feeling unwell.
Here are four everyday things that might be stealthily dehydrating you:
Diet Pills & ‘Fat Burning’ Supplements
If you’re taking weight loss supplements or diet pills, be warned – many of these products are diuretics and instead of causing fat loss, simply flush water out of your system more quickly. There’s a big risk of dehydration when using these products, including many ‘slimming’ teas and herbal medicines.
The bottom line: always consult with a health practitioner before using any ‘weight loss’ supplement. It’s critical to ensure they’re safe to take and that you’re aware of any side effects.
Too Much Coffee & Tea
Keep an eye on your intake of caffeinated liquids, too – overdoing it on coffee or even green tea can dehydrate you faster. Caffeine is a diuretic, causing you to go to the bathroom more frequently and speeding up fluid loss.
Coffee, black tea, green tea, soft drinks and energy drinks are all culprits in dehydrating you. If you’re drinking anything caffeinated, make sure you’re getting enough water as well, rather than relying on caffeinated drinks for your fluids.
Some common herbal teas also have a diuretic effect, including dandelion, hibiscus and ginger.
Hot, Humid Weather
I know this one is obvious, but if you check out the news around festival season each year, you’ll discover an epidemic of heat-related illnesses. Hot weather can lead to something called ‘insensible water loss’ – basically, you’re losing fluids without realising it.
Sweltering temperatures increase sweating as the body tries to cool down itself, even if you’re not physically active. Humid, tropical climates make this even worse, as it’s harder for sweat evaporation to lower our temperature.
It’s easy to forget about staying hydrated when we’re having fun in the sun (especially if there’s day drinking involved). Heat stroke is all too common when people lose track of their water intake – so when you’re outdoors in summer, keep that water bottle handy!
Improper Exercise Hydration
You’d be surprised how many people aren’t properly hydrating for their workouts, even when they’ve been training regularly for years. Notably, you shouldn’t wait until during or after your session to drink water – pre-hydration is the key.
Dehydration can occur in just 30 minutes when exercising, so keep an eye out for symptoms. Check the colour of your urine, too – if you’re already dehydrated before you start sweating, you’re not far from feeling the effects.
Can I Stay Hydrated Without Drinking Water?
Not all your fluid needs to come from plain water, but it should be your main source of fluids. Other beverages (and foods with a high water content) still help you stay hydrated, but there are two reasons they shouldn’t be your only fluid intake.
Some drinks are diuretics, which have a dehydrating effect on the body. Diuretics include alcohol, coffee, caffeinated tea, some herbal teas, energy drinks and soft drinks. These still count towards your fluid intake but aren’t as effective as plain water.
Sugary drinks are high in calories, so sipping on sweetened drinks all day adds up! For example, a 350ml glass of apple juice is equivalent to eating 7 sugar cubes! Multiply that by eight glasses, and that’s 4720kj – about half your daily energy intake.
Adding so many liquid calories to your diet makes it difficult to maintain a healthy weight, especially when you aren’t getting any fibre or protein to fill you up. That’s why sugary drinks are a dangerous source of ‘calorie creep’ – they’re all too easy to guzzle down.
If you struggle to drink a lot of plain water, here are five tips to help you increase your fluid intake:
- Boost your hydration at mealtimes with bone broths and soups
- Snack on fruit and veg with a high water content (like melon, pineapple, celery and cucumber)
- Add a healthy smoothie to your daily meal plan
- Flavour your water with fruit slices or mint to keep it interesting
- Try sparkling water – you can add carbonation to tap water with a SodaStream
These shouldn’t be a substitute for drinking water, but they can help increase your hydration levels. Research shows that, on average, about 30% of our fluid intake comes from food – but that still leaves the remaining 70% to top up.
If you can find a way to enjoy (or even tolerate) water, you’ll be doing your body a lifelong favour!
Next Steps
Looking to build healthier habits into your daily routine? Forget the expensive supplements and health foods – if you’re not already drinking enough water, that should be priority number one on your list.
If you’re eager to increase your fluid intake but are struggling to hit your goal, here are a few handy tips:
- Get a big glass of water with every meal and snack (this helps avoid overeating, too)
- Carry a reusable water bottle with you throughout the day
- Set regular reminders on your phone or work computer
- Track your water intake using your fitness tracker or an app
- Start your morning with a glass of water (a great energy booster!)
- Team up with a workmate and keep each other accountable
Keen to learn more about healthy hydration? Go ahead and check out these articles:
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