Hydration, dehydration, and overhydration basics for active people

When it comes to being healthy and to performing our best, our main focus is usually what and how much we eat. However, at least as important as the nutrients we carefully choose in our diets are our water intake and hydration strategies.

You’ve probably heard that we’re made up of water. If you’re an adult male, you’re probably 60% water. If you’re an adult female, you’re around 55% water. And if you’re an infant reading sports blogs, you probably already know you’re 75% water.


But why does it matter?

Dehydration can have some nasty consequences – nausea, headache, low blood pressure, fatigue, increased heart rate, constipation. Hell, you can even die if you lose 10-20% of body water. You don’t want that.

When it comes to sports, almost all endurance athletes experience symptoms of dehydration during a training or a race. Besides the obvious fatigue, this means cramps, increased blood thickness, dizziness, everything leading to decreased performance.

Dehydration by only 2% of body weight is enough to decrease exercise performance.


How much water do you need?


The rule of the thumb is 30-40ml/kg of bodyweight. Or somewhere between 2-3 l/day. This includes what we drink as plain water, and also the water we take in from food.

You can get a picture about the water content of some foods based on the chart below:



But you really don’t have to be good at math to figure our if you’re drinking enough water. Tracking your water intake is not necessary, either.

Just drink if you’re thirsty. Unless you’re running for longer than 40-50 minutes on a summer day, and then yes, you should have a sip.

Keep in mind that we are all different and have different needs. Our water intake needs are influenced by humidity, ambient temperature, effort etc.

Some – I’m talking more about sedentary people – are ok with 2 liters of water a day and eating foods that are also rich in water content.

Others, of course, need more water. Endurance athletes can go up to 6l/day. And if we’re talking about physique contests or sports that involve weigh-ins, then body water manipulation becomes a mathematical art.

The simplest and most eloquent hydration test is the urine colour. Based on the chart below you can tell where you stand.






For moderate effort lasting under 2h or intense effort of less than 1h, the general rule is to have 0,5-1l of water during your activity, the same after you end it and 0,25-0,5l with every meal.

For intense effort lasting more than 1h or moderate effort lasting more than 2h, it’s enough to have 0,25-0,5 l of water 30-60 min before your workout, and for every hour of exercise add 600 ml of water with a mix of carb (30-45g), protein (15g) and electrolytes. That should also be the numbers for your recovery drink, and besides these, having 0,25-0,5 l of water with every meal also applies.


How much water is too much?


You’ve probably heard a million times that you should drink more water. But has anyone told you that drinking too much of it is as bad as not drinking any?

Too much water can cause hyponatremia, meaning low sodium levels in your blood. Just like dehydration, hyponatremia can be lethal. It’s a condition caused by a high water intake, but not enough minerals to replenish those lost.

If you’re doing some sports, you’ve probably heard about electrolytes. They’re more than flavoured fairy dust that you add to your water to crush a workout or a race.

Electrolytes are minerals – sodium, potassium, calcium, magnesium – that carry an electric charge when they are dissolved in water. What this means is that they are electrical transporters for fluids through cell membranes. We usually lose them through sweat and urine. That’s why it’s important to make sure that, during long trainings or competitions where we sweat a lot, we provide the body with electrolytes as well, not just loads of plain water.

Too much plain water without adding electrolytes can throw off the body’s fluid balance.

So here’s what adding electrolytes to your drink will get you:

  • more rapid absorbtion of fluids
  • improved endurance
  • improved immunity
  • increased blood and muscle glucose, as well as glycogen synthesis
  • optimal hydration


Hydration basics for endurance athletes


If you’re a runner or any other kind of endurance athlete, here’s what you should be paying attention to:


  • Follow the instructions of your isotonic drinks and use as much water per measure as the label says to. When in doubt, it’s better to make it more diluted because concentrated drinks can cause stomach problems and they will also be absorbed slower. The concentration should be less than 10%.

  • Don’t drink too much at once. Smaller sips are always better than pouring half a litre of drink down your throat. Your body needs to process it, so drinking too much at once can leave you bloated. And that feeling of going downhill with a belly full of water is horrible, and you know it.
  • Add a pinch of table salt to the water you have during trainings. It will help your body use it more effectively. Or have some pickles. Pickles <3 forever.
  • In the days before a race, make sure your urine is clear yellow (levels 1-2 on the chart above).
  • Don’t wait until you’re thirsty to drink. That doesn’t mean overdoing it, but just a sip of water every 20 minutes or so, depending on the intensity, distance, temperature etc.
  • You can also add some protein to your carbohydrate & electrolyte recovery drink, to make sure you support protein synthesis and you have less protein breakdown as a result of your training. It’s great for feeling less like you’ve been run over by a bus after a training.
  • If you find it hard to drink during a race that lasts longer than 1-2 hours (either because you don’t tolerate sports drinks or any kind of liquids in your stomach, or because you’re a competitive mofo and you don’t want to waste time in the refreshment points), the least you can do is make sure you’re hydrated enough at the start and train a few times without water, in relatively similar conditions, to see what you can handle.
  • A higher carb diet will make you store more water (3-4g of water per g of stored carbohydrate). It’s important to know that when you do carbo loading. As amazing as all you can eat pasta for a week might sound, it might leave you with some extra water weight to carry up the hills.
  • Before the menstruation, women retain more water and feel puffy. It’s normal and it’s caused by a hormone called aldosterone that decreases urinary output. You’re not getting fat 🙂


Try this to drink more water


If you feel like you’re not drinking enough water, here’s what you can try:

  • keeping a big bottle of water on your desk at work,
  • using an app that monitors your intake (you can use a food logging app such as MyFitnessPal or one just for water ), or just set your alarm often enough,
  • if you’re bored of plain water, make some tea, infused water, lemonade. Get creative.
  • eat more foods with a richer water content.


And, bonus: shakes, soup, coffee etc – they all have water, so they count. 🙂


So that’s about it, but if you have any other questions, let me know.




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