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Ever wondered what happens to your body if you don't get enough water? Our bodies are mostly water by weight, so in today's episode of SciShow Hank explains what happens to your body as it starts to shut down when you go without that tasty H2O.

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Just a little while ago we were talking about what your body goes through without food, and I mentioned that a person can live for weeks without eating, and yet we're lucky enough to get a few days without water. So what's the difference?

Part of the reason why we're always dumping more liquid into our bodies is because we basically are water, 50-70% of your body mass is water, and as much as 75% of that bodily fluid is tucked away in your cells, which are, in one way or another, responsible for everything you do. 

Your body fluid is mostly water, plus a whole lot of electrolytes which are dissolved ions of minerals like sodium, calcium, magnesium and potassium. Concentrations of each kind of ion charge up the fluid on either side of your cell membranes, and it's that charged separation that your cells use to regulate your body's electrical system, which is what your muscles and nerves use to think and move and break dance and stuff.

In addition to providing this very worthwhile service, your body fluid does a ton of other stuff you need to live. It helps regulate your body temperature by providing sweat, ferries blood cells and nutrients all over the body, keeps food moving through your guts and helps flush out all the leftover waste products. So you can see why, whether you've been chasing a ball in the sun or you have chronic diarrhea or your runaway camel just left you stranded in the desert, it's very important to listen to your thirst.

If you've got cotton mouth, and you're flushed and feeling super thirsty you're probably already mildly dehydrated, meaning your body fluid is running low by about 2%. This first stage is very easy to remedy, just drink a couple glasses of water. But, if you're too oblivious or sick to drink, or don't have access to potable liquids in the middle of the desert, you're going to start sliding off into the next phase: moderate dehydration. 

If you pinch your skin and it doesn't snap back right away, it stays, like, tented up there, you are failing the Turgor Test, you're basically starting to shrivel up. You are now missing 5-10% of your necessary bodily fluid. Your head is pounding, you feel nauseated, you're probably hot and confused, your brain is starting to feel all fuzzy. That's because it's mad at you, you're basically draining it's comfy water bed. If you're down by over 10% of your fluids, things are getting dire- you have rolled into severe dehydration. 

Your eyes will start settling into the back of their sockets, your pee is gonna look dark and scary, and will probably be painful, if you can even go at this point. Your muscles are cramping, you may start shaking and you'll be feeling super tired and like you're dying a little bit. Mostly because you're dying. Your blood pressure is dropping as your shrivelling cells desperately try to get fluid. You've lost too many of your electrolytes, mostly through sweat and urine, and without the right electrolyte balances your cells can't maintain the voltages they need to activate muscles like your heart. Low sodium levels can also cause your brain to swell.

By now you're well beyond the point of needing a glass of water, you probably need an ambulance, a slow IV of electrolyte fluid and a good amount of luck. And for all of you inquiring minds probably wondering about the value of urophagia or pee drinking: while technically you can  drink your own urine at least once, it isn't recommended when you're already very dehydrated. A properly hydrated persons pee is mostly water, but the water-to-waste ratio gets skewed the longer you go without drinking, so a dehydrated persons urine has a lot of waste in it, and by drinking it you're making your already endangered body work harder to filter it all over again, which just isn't worth it, and it's pretty gross.

So, stay hydrated! And thank you for watching this episode of SciShow, and a special thanks to all of our subscribers on subbable, you could have an honorary SciShow title like associate producer or president of space, to learn about these and other excellent perks go to, and as always you can reach us on facebook and twitter, and in the comments below. And if you wanna keep getting smarter with us, don't forget to go to and subscribe.