Dehydration: What happens to your body when you don’t drink enough water?
People can’t live without water. It makes up 50–70% of our body weight and is important for almost every bodily function. We can feel awful if we don’t have enough water in our bodies. This can happen if we’re dehydrated, sick, work out a lot, or are under a lot of heat stress. At first, we’re thirsty and tired, and we might get a mild headache. This leads to grumpiness and mental and physical decline in the long run.
We lose water all the time through our breath, urine, poop, and skin. Most healthy people control the amount of water in their bodies very well by what they eat and drink, guided by their hunger and thirst. But this is harder for babies, sick people, old people, athletes, and people with physically demanding jobs, especially when it’s hot.
What does it mean to be dehydrated?
By the time you feel thirsty, your body is already dehydrated. Our thirst mechanism is behind our actual level of hydration.
Research has shown that even 1% dehydration can hurt your mood, attention, memory, and ability to move around. Human data is limited and sometimes contradictory, but it seems that dehydration makes brain tissue fluid decrease, which reduces brain volume and temporarily changes how cells work.
When you don’t replace the water you “lose,” your blood becomes more concentrated, which makes your kidneys hold on to water. The result is that you pee less.
The thicker and more concentrated your blood gets, the harder it is for your heart and blood vessels to make up for it by increasing your heart rate to keep your blood pressure steady. When your dehydrated body is “pushed,” like when you work out or face heat stress, you are more likely to get tired or pass out. This can make you pass out if you stand up too quickly, for example.
Less water also makes it harder for the body to keep its temperature steady, which can lead to hyperthermia (a body temperature greatly above normal). At the level of the cell, “shrinking” happens when water is used to keep other stores, like the blood, full. The brain can tell this is happening, so it makes you feel thirstier.
How many drinks should I have?
Normal water needs vary a lot from person to person because of things like body size, metabolism, diet, climate, and clothing.
Surprisingly, the first official advice about how much water to drink didn’t come out until 2004. The Institute of Medicine says that adult men and women should drink 3.7 and 2.7 liters of water each day, respectively.
About 80% of the water you need each day should come from drinks, whether they are water, coffee, or alcohol. and the other 20% comes from food.
This is just a rough guide, though. Here’s how to keep track of your own water intake:
Keep track of your weight and stay within 1% of your normal weight. You can find your baseline by taking the average of your weight right after getting out of bed and before breakfast on three separate mornings.
Monitor your urine. You should go to the bathroom more than three or four times a day, and your urine should be a pale straw or light yellow color and smell mild. If they are less frequent, darker, or smelly, you should drink more water.
Make sure you’re getting enough fluids. If you drink enough water, you shouldn’t feel thirsty.
