How does diarrhea kill someone?

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I have heard that it dehydrates you to death, but couldn’t you just keep drinking water? Even before modern medicine I’m sure water wasn’t impossible for people to get.

Edit: Thank you for the simple answers! In hindsight, I feel kind of silly not realizing that you need to ABSORB the water…

In: Biology

With chronic diarrhea you wind up passing the water through you before you can absorb enough.

If you didn’t have access to a clean source of water, i.e., it’s what was causing the diarrhea to begin with, then drinking more of it isn’t going to help any. Severe cases can last for days and drain you of a *lot* of water, more than you might be taking in from drinking alone. And it is oftentimes a symptom of other more serious infections that are doing other things to your body in the meantime.

diarrhea is you not absorbing water.

you can keep drinking it, but it just comes out the other side (as diarrhea)

It is not just the water, it really becomes the loss of electrolytes that is problematic after some time or if the diarrhea is severe enough.

And before you ask, no – Gatorade or other electrolyte waters won’t be enough to restore normal electrolyte balance in moderately severe or worse diarrhea.

Even in a best case scenario, if you were to try and restore what you were losing by drinking lots of fluid, it gets to a point where you can’t consume enough fluid with electrolytes fast enough to keep up with losses, or you cause more electrolyte abnormalities by drinking too much “pure” water. This is why when you go to the hospital for severe diarrhea or dehydration, we use intravenous fluids which have high concentrations of certain electrolytes in them (usually salt, others have potassium, sodium bicarbonate, and different ratios of sodium chloride)

Just a little add on at this point, but serious illness that cause diarrhoea can also cause vomitting and sweating that will cost you even more water and electrolytes. Also dirty water is often the cause for illness like cholera so drinking more dirty water will just make you sick for longer.

Diarrhea doesn’t just cause loss of water it also causes loss of electrolytes and secretory fluids from the Gastrointestinal track which can ultimately lead to build up of acid in the blood. Everything combined i.e. Dehydration, Electrolyte Abnormalities and Acidosis can lead to death.

Diarrhea generally kills people (mostly kids) by severe dehydration leading to kidney failure, which interrupts the kidney’s ability to maintain a neutral pH in the blood. The resulting acidosis is what kills most people. The dehydration comes from the inflamed intestines becoming “leaky”, spilling out a bunch of water mixed with electrolytes and proteins from the bloodstream into the intestinal tract.

Drinking lots of water can go a long way to offsetting the fluid losses in diarrhea. The problem is, you’re losing not just water, but also electrolytes (most importantly sodium but also potassium) through the gut. If you replace the water without replacing the sodium, you will basically dilute out the sodium in your body. A very low sodium level primarily affects the brain, causing confusion, eventually leading to seizures, coma, and death. This is the other way you might die from diarrhea.

Contrary to what a lot of people are saying in this thread, the first-line treatment for severe diarrhea is [oral rehydration therapy (ORT)](https://en.wikipedia.org/wiki/Oral_rehydration_therapy). The gut will absorb water even with active diarrhea and even with moderate vomiting. However, plain water isn’t enough. You also need sodium and potassium to replace losses from the gut. Citrate is commonly added as well (it is converted in the body to bicarbonate to act as a pH buffer and decrease acidosis). Glucose is also added, because the sodium is absorbed via a sodium-glucose co-transport protein. ORT has decreased mortality from diarrheal illnesses by up to 93% in settings where it’s been implemented. Only in cases where there’s truly intractable vomiting or decreased level of consciousness is IV rehydration necessary.

Just to note, sports drinks like Gatorade are *not* the same as ORT. They are formulated to replace losses from sweat, which is very dilute compared with diarrheal losses, and also add in about 4-5x as much sugar as ORT, so it tastes good. You’d be better off with an electrolyte solution like Pedialyte, or mixing your own ORT with table salt and sugar.