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5 terrifying things that can happen to your body when you're dehydrated

Water bottle
Dehydration can lead to big problems.
Michael Dodge/Getty

The INSIDER Summary:

  • Your body can't function without water.
  • In severe cases, not drinking enough water can lead to serious complications.
  • These include drops in blood pressure, increased heart rate, feeling faint or confused, or having seizures.

Water makes up about 60% of your body — and every single cell inside it needs water to work properly. That's why staying hydrated is so important. 

Luckily, mild cases of dehydration are easy to spot and easy to treat — all you have to do is drink some fluid. Severe dehydration is another story. Left untreated, it can lead to complications that require immediate medical attention.

Here's what can happen to your body in more serious cases:

Your heart might race.

"If you're dehydrated, your blood volume decreases and blood pressure also goes down," dietitian Andy Bellatti, MS, RD, told INSIDER. "As blood pressure goes down, heart rate increases."

This might make you feel lightheaded, weak, or tired, and you could experience to a pounding or fluttering feeling in your chest. (If that feeling persists after you drink some fluid, by the way, you should get medical attention.)

Your blood pressure could drop dangerously low. 

doctors office wall
Flickr/Andrew Malone

In the most severe cases, blood pressure and blood volume can drop so low that the body goes into a state called hypovolemic shock, according to the Mayo Clinic. That's when the heart is unable to pump enough blood to the body, and organs start to shut down. It's a life-threatening complication that needs immediate emergency treatment.

But it's worth noting again that this only occurs in extremely severe cases of blood or fluid loss. Sweating during your morning jog, for instance, will make you lose fluid, but it isn't going to send you into hypovolemic shock.

You could up your risk for kidney problems (over time).

glass of water
Flickr/Michael Hamann

The odds of getting painful kidney stones can go up if you are dehydrated again and again and again.

"When you're dehydrated, the kidneys get a signal to retain more water and you start urinating less," Bellatti said. "And we do know that one of many factors that can increase kidney stone formation is when urine is [concentrated]." 

The Mayo Clinic also adds that "prolonged or repeated bouts of dehydration" can lead to urinary tract infections and kidney failure.

You could have confusion or seizures. 

Electrolytes are minerals with an electric charge — potassium, calcium and sodium are some of the best-known ones. You get them from your diet and they help carry electrical signals between cells. But when you're dehydrated, your electrolyte balance can get thrown off. Bellatti explained this imbalance can make you feel faint or confused, and in severe cases, it can lead to seizures.

If you're experiencing these symptoms and you haven't urinated in 12 hours or so, Bellatti said, you should get to an ER: That kind of dehydration requires immediate treatment with IV fluids. 

If you're in the sun for a long time, you could get heat stroke. 

woman sunbathing tanning sun
Flickr/Dean Hochman

Heat stroke — the most serious form of heat injury — can happen after long, extreme sun exposure, when the body isn't able to cool itself down enough. Symptoms include confusion, dizziness, rapid heartbeat, loss of consciousness and more. This is another condition that requires immediate medical attention and can be life-threatening.

Where does dehydration come in? In order for our bodies to stay cool, they need to sweat. And if you're dehydrated, you may not be able to sweat enough to cool yourself down. Staying hydrated is one way to prevent heat stroke

It all sounds very scary, but Bellatti stressed that most people aren't going to be at risk for these complications. 

"The only people who really need to worry about true dehydration, I would say, would be anybody who's engaged in high endurance physical activity for long periods of time, especially in the heat," he said. 

And remember: Preventing dehydration is really easy. Just tune into your body and make sure to drink fluids when you feel thirsty.

"Thirst is there for a reason," Bellatti said. "So as long as you listen to it, you should be fine."

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