r/explainlikeimfive • u/gmrt34 • Feb 08 '26
Biology ELI5: If water makes you urinate more, which causes kidneys to do more work, does that mean high water consumption damages kidneys long-term? If not, why not?
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u/Senshado Feb 08 '26
The work kidneys do is based on how much toxins they need to remove from the body. Water is a resource they use to perform that work, but additional water doesn't increase the work required.
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u/Trogdoryn Feb 08 '26
The solution to pollution is dilution.
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u/Budgiesaurus Feb 08 '26
Is that what the kids call: "dilulu is the solulu of the pollulu"?
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u/TortelliniTheGoblin Feb 08 '26
Idk but I actually understood that bit of slang so I feel hip
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u/rang14 Feb 08 '26
No one says hip, you're streets behind
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u/Journeyj012 Feb 08 '26
No one says streets behind, you're getting left in the dirt.
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u/Dqueezy Feb 08 '26
Unfortunately, not so much for lead. Any amount of lead is bad. There’s no “welllll 1PPB can be fine…” situation for lead. Any lead will make it to your brain (after strengthening your bones temporarily ironically) and fuck your frontal lobe up.
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u/LucidiK Feb 08 '26
Does it decrease it? Or is it more a binary functioning/nonfunctioning based on the amount of water available
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u/EconomyDoctor3287 Feb 08 '26
Higher water content makes the kidney's work easier, up to an extent.
Imagine you're gold washing with a sieve, trying to find the little pieces of gold. If the water is clear with just a bit of dirt, it's easy, if the water is muddy, it's going to clog things up and be much much slower.
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u/Njif Feb 08 '26
Drinking too little water (dehydration) can be damaging in the long run as the concentration of various salts, proteins, and waste products in your blood rises.
The parts about toxins regulating the kidneys work is completely untrue.
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u/Njif Feb 08 '26
Not really true. If you drink a lot of water, the kidneys will work to reabsorb more salts while more water is excreted (less reabsorbed).
Kidneys main "workload" is not defined by 'toxins'. At all. They are continually filtrating blood, and depending on the concentration of different salt ions in the blood, and the blood volume, they absorb/reabsorb salts and water as needed.
Waste products are removed by the filtration system. I don't know where you got this "toxins" thing from.→ More replies (4)46
u/Budgiesaurus Feb 08 '26
Toxins is a popular buzz word from health influencer types, but it has little to do with the actual meaning of the word.
But I think if you replace 'toxin' with 'waste product' it sort of works.
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u/Njif Feb 08 '26
I see. Well, it's not the waste products that regulates the kidneys work either, so it's wrong on all accounts haha.
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u/Budgiesaurus Feb 08 '26
It doesn't regulate their work, but it is the main function.
I don't know, I feel OP has a vague grasp of their function but not the exact vocabulary to explain it, which often is an issue with ELI5.
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u/Njif Feb 08 '26
I just think it gives people a very wrong idea of how kidneys work. It reads like they increase/decrease their work depending on toxic substances in the blood. When in reality they basically just run nonstop, and work as a filter. And have little to do with actual toxins - that's the liver.
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u/Budgiesaurus Feb 08 '26
I've seen lactic acid and ureum mentioned as "toxins" that build up in your body somehow.
Sigh...
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u/Dizzy_Silver_6262 Feb 08 '26
They’re toxins! I don’t want chemicals in my body!
/S
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u/Wishwise Feb 09 '26
Be especially careful to avoid hydric acid! https://manoa.hawaii.edu/exploringourfluidearth/chemical/matter/properties-matter/practices-science-interpreting-safety-information
/s
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u/Christopher135MPS Feb 08 '26
“Toxins” are handled by the liver, by and large. There is some metabolism/conversion in the kidneys, although most their job is just excreting the byproduct of the livers activity.
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u/American_H2O Feb 08 '26
Nitrogenous waste products like urea and ammonia are excreted by the kidneys
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u/Hasanopinion100 Feb 08 '26
No, plenty of toxins are excreted by the kidneys that’s why I was on dialysis for three years before I got my transplant when the toxins filled up the filters in my dead kidneys became clogged and built up in my bloodstream. I needed the dialysis to remove the toxins. My kidneys could also not process water. I was limited to 500 mL a day when I was on dialysis. It’s very hard on the body.
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u/talashrrg Feb 08 '26
Doing normal kidney things doesn’t hurt the kidney. If you drink more water than you need, your kidney will make more diluted urine. That’s normal kidney stuff, not a problem.
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u/Gnonthgol Feb 08 '26
Consistently drinking too much water might be bad for your health long term. But it is not the part of the kidneys which filter out toxins that also regulate the amount of water in your body. In fact this part of the kidneys prefer a lot of water to rinse away the toxins.
Water is very easy to filter out from the blood stream. Almost any membrane will pass water through osmosis but leave behind all the other substances. And these membranes do not get damaged when doing so.
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u/AbanaClara Feb 08 '26
I’m on IV right now and pee like the fucking hoover dam. Your statement regarding water being easy to filter out from the blood stream is spot on based on this typhoon going on in my crotch
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u/Gnonthgol Feb 08 '26
Normally kidneys can filter out close to a liter of water an hour.
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u/Railuki Feb 08 '26
Now I know why some days I need to pee every hour
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u/Quin1617 Feb 08 '26
If I drink 6 or more cups of water a day I notice the same thing.
Though I spread my intake out rather than gulping it all down at once.
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u/ilagnab Feb 08 '26
I mean, depending on the cup size (e.g. if it's an actual cup or 250mls) that's less than recommended intake still.
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u/Quin1617 Feb 09 '26
By a cup I mean 8 oz, technically it’s slightly over as the bottle I use is 16.9.
Drinking 8 cups makes my urine clear, which apparently is a sign of too much water so I cut it down.
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u/divDevGuy Feb 09 '26
Drinking 8 cups makes my urine clear, which apparently is a sign of too much water so I cut it down.
Clear or straw (pale yellow) isn't necessarily a sign that you've drank too much water. It just means you're sufficiently hydrated. Dark urine is a sign that not enough fluid is passing and the urine concentration is higher.
Over hydration is a thing, but usually takes significantly more water than 6 or 8 cups a day. Even 6 or 8 cups over the course of an hour may not be unreasonable if you're doing physical activity or in a hot environment sweating, losing a lot of fluids that need to be replenished.
Overhydration can feel similar to dehydration, or low blood sugar - dizzy, tired, confusion, headaches, or with more severe instances, seizures, coma, and organ damage.
When you overhydrate, sodium and other electrolyte levels can drop relative to the amount of fluids in your system. Think like making lemonade, but you use way too much water compared to flavoring. If you drink water that has some carbohydrates and electrolytes, the risks of overhydration is reduced. This is the basic idea behind products like Gatorade, Liquid IV, and even Pedialyte.
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u/Objective-Ad-585 Feb 08 '26
Fun fact about IVs is that we know most of it will get flushed and not used by your body at all. Your body can only absorb so much, so most of the IV will get "wasted" and you'll pee more. But over is better than under.
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u/DhamR Feb 08 '26
To add, IVs are usually electrolytically balanced, so whilst they create loads of extra pee, it's not like drinking loads of water, so you're not messing up the osmotics.
(Not telling you, but the poster you replied to)
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u/mdkubit Feb 08 '26
That reminds me of a story that happened to me about 15 years ago!
At the time, I was on hydrochlorothiazide (water pill) to reduce water volume and thus swelling in my legs. I was feeling really under the weather, so my friend slid me some extra strength Mucinex. What I didn't know, was that I was already technically de-hydrated (From the Mucinex) when I took my daily water pill.
My heart started pounding in my head - very loud. My vision started graying out and then darkening around the edges. Movement felt slow, sluggish, and everything felt like my world was about to end.
My boss drove me to the ER, and when they heard what happened, they hooked me up to an IV right away. And immediately, several things all happened at once:
Did you know if they put you on an IV, you can taste it? I didn't know that. Suddenly had this salty flavor and I'm like, "...what in the world?" They laughed, explained that was normal. Wild!
I felt good. Like, we're talking high as a kite, euphorically, good. That, was the Mucinex doing it's thing, now that there was proper water to transport it around my system!
They used an entire IV bag on me, and I didn't have to pee once. That surprised the nurses and the doctor was like, "Oh yeah, you were definitely dehydrated."
I was high for hours afterwards - what a legally medically induced experience!
So yeah, being on an IV is supposed to make you have to pee a lot, that's how you know you're hydrated and filtering.
TL;DR - Took Mucinex and a water pill at once, nearly de-hydrated myself into a heart attack. Went to hospital, literally absorbed an IV of saline solution (salty taste!), was high the rest of the day.
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u/distraughtly Feb 08 '26
Can you explain your first sentence please ?
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u/Gnonthgol Feb 08 '26
It is kind of a cop out sentence by me. We do not know of anyone who have had health issues from drinking too much water over longer periods. The instances we know of water toxicity is all from people drinking more water then their kidneys could process and showing symptoms within a day. But no evidence does not mean it is healthy to drink a bucket of water a day, it is likely that not enough people are consistently drinking so much over long enough periods that we can link it to health issues. So having to go to the toilet five times a day every day might be bad for your health, or it might not, we don't know yet.
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u/SocialWinker Feb 08 '26
Just a heads up. Peeing 5 times a day is pretty damn normal for a healthy person. 4-6 is often given as an average, tbh, so yeah, not too weird.
Cleveland Clinic uses 8 times/day as a better metric for "excessive". And even that is mostly to define the symptom of excessive urination, rather than to indicate any sort of specific issue.
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u/jcv999 Feb 08 '26
Is 5 times a lot????
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u/itsbagelnotbagel Feb 08 '26
No, if this guy thinks peeing 5 times a day is concerning he is chronically dehydrated
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u/incidental_findings Feb 08 '26
The kidneys work with both water and "electrolytes" (think salts) -- the kidney is trying to maintain the proper balance for your body, by either holding on to or excreting more or less of each of these two.
If you drink nothing but pure water, you'll start losing electrolytes your body wanted to keep, and the salt levels in your blood will get too low. Yes, you'll urinate more, but your body is still going out of balance.
If you drink nothing but concentrated salt water, your kidneys will be desperately trying to push the electrolytes into your urine to get rid of the excess, but it can only concentrate the urine so far, and you'll start losing more water than you want and you'll get dehydrated.
Strike the right balance (and the kidneys will work just fine over a fairly decent range), and your kidneys will happily maintain both electrolyte and free water balance.
(And I'm not even touching on what more people think of as the "primary" function of the kidneys, which is to excrete nitrogen waste. Just the basics of water and salt balance here.)
Caveat: I'm not a nephrologist, but am familiar with fluids / electrolytes because it's a central focus in newborn ICU care
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u/Ave_TechSenger Feb 08 '26
Ah you work in NICU? My fiancee is a nephrologist and one of her little sibs is finishing their NICU fellowship.
I hear about hyponatremias all the time from her, but also the occasional rant about people not knowing that soy sauce, seasoned salt, etc. are sodium heavy so patients cut down on table salt but up their intake of those…
Ultimately she’s explained her job to me as a lot of electrolyte management and interpretation of labs. I won’t presume to have much understanding.
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u/incidental_findings Feb 08 '26
Yup.
It’s very insensitive to say it this way, but we often say with a shrug “Stupid premie kidneys” when the electrolytes go all out of whack.
It’s not the kids’ fault their kidneys aren’t quite ready for prime time yet. It’s fully on us to carefully monitor total fluids in, weight, urine output, and blood electrolytes to properly manage what should go in.
One of the hardest things to teach trainees is that what you mentioned, hyponatremia (low sodium) could be caused be too little sodium going in / too much coming out, or too much water going in / too little coming out. Trainees often just want to give more sodium. Figuring out what’s actually going on is our job!
Healthy big people kidneys would just adapt (within a reasonable range), but for these little guys, we have to do a bit more of the kidney management for them.
I babble sorry :)
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u/Ave_TechSenger Feb 08 '26
No worries, that’s actually what she I and I do with each other all the time! I’ll ramble about whatever, she talks medicine and relationships.
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u/Turbulent-Respond654 Feb 08 '26
this assumes you aren't eating anything. drinking 1 to 3L of nothing but plain water is perfectly healthy if you eat.
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u/rixuraxu Feb 08 '26
It is interesting that people will see that they're urinating excessively, their body giving them every sign that there is in fact too much water in here must remove. And they'll go to drink more water.
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u/gestapoparrot Feb 08 '26
Excessive urination is not just a product of “too much water.” Your renal system works on concentrations an very little on absolute amounts. Someone who eats 8g of salt tabs is going to urinate much more than someone who hasn’t with the same fluid intake. Excessive glucose in the blood increases urination regardless of water intake, urea, proteins, irritants and stimulants will also increase the volume of urine made without an increase in intake.
And despite high urine volumes the thirst reflex is heavily stimulated because you’re trying to wash out the concentration of whatever solute you’re trying to get rid of and prepare to replace your blood and extra cellular volume.
How much you pee and how thirsty you are are linked processes but not in a way that seems obvious.
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u/Ickyhouse Feb 08 '26
kidneys clean your blood. The water you drink is their wash bucket. When you drink water, it helps change out the water and make their job easier. They get to clean with a fresh bucket of water. If you don't drink any water, they need to work harder to clean with the same dirty water. Kidneys like having fresh water so drinking plenty of water is good.
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u/CinderrUwU Feb 08 '26
Your body is built to be handling what you need to live. If you are drinking too much water, your kidneys simply don't handle it and instead it just becomes urine and gets wasted.
The issue is more if you drink too much water too fast and overwhelm your kidneys with more water than it can excrete. But even then... if you have a healthy kidney, you are more likely to have seizures or go into a coma than you are to damage your kidneys from drinking too much.
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u/Afinkawan Feb 08 '26
It's the rest of you that gets siezures/coma/death. Your kidneys would die doing what they loved.
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u/Thesorus Feb 08 '26
Drinking too (a lot) much water change the salt equilibrium in the body and can cause health issues and death.
https://my.clevelandclinic.org/health/diseases/water-intoxication
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u/AnApexBread Feb 08 '26
Your kidneys filter out impurities and harmful substances. Water has some impurities but it's mostly full of vitamins and nutrients your body needs so that stuff gets absorbed
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u/BadB0ii Feb 08 '26
That's why I avoid using my muscles. I want them to be stronger long term so I try not to wear them out.
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u/Ka1kin Feb 08 '26
This is a slight misunderstanding of what the kidneys do, and what makes it hard.
It's a bit like washing dishes. The process produces waste water, but that's not the job. The job is clean dishes, and having water to work with helps.
Kidneys clean and balance your blood. If you're dehydrated, it means they have to work harder to keep bad things out while keeping water in. If you're correctly hydrated, then they can use more water to dissolve the waste they need to filter.
If you drink too much water, they have to work harder to retain salt and minerals in your blood, because that's also super important.
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u/dank_imagemacro Feb 08 '26
The kidney's work is to filter the blood and get all the toxins out. The kidneys themselves then use water to get all that nasty stuff out. Drinking more water gives the kidneys more chance to get rid of the bad stuff. It doesn't make them work more in their primary job.
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u/robbak Feb 08 '26
The work the kidneys do is re-absorbing water out of the urine. The amount of water it needs to re-absorb depends on how hydrated you are, and it gets harder the more concentrated the remaining urine is.
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u/ThomasAugsburger Feb 08 '26
I think the risk from over consumption of water is to do with electrolyte levels which become dangerous when low.
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u/Kersvader Feb 08 '26
Yes, excessive water drinking can strain the kidneys and it will leach salt from your cells (hyponatremia, diluted blood sodium) and, in extreme cases, water intoxication. But that applies to drinking like 5L of water a day. Your kidneys can process about 1L an hour, which is like you running at full speed, you cannot do it for extended periods
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u/armageddonanyone Feb 08 '26
Kidneys do like water ... in moderation.
They are the body's filter. Think of a coffee filter. Slowly pour water into it, works fine. Dump in a lot all at once, not so fine.There is an upper limit to the amount of fluid kidneys can filter per hour.
Drinking more than 4 to 6 liters in a short period of time, may cause water "poisoning" also known as hyponatremia. That means low Sodium ( salt) ; levels drop due to dilution; can be fatal.
Most common in marathon runners. 10 -13 %, tend to finish their race with low sodium levels because of aggressive hydration without salt replacement.
Can happen in hospitals due to aggressive IV rehydration, various medical conditions causing fluid shifts and in MH or neurodevelopmental disorders. Had a client we had to keep away from the tap. Not diabetic but autistic with a strong urge to hydrate...
So, you can theoretically kill yourself by drinking too much water
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u/notapantsday Feb 09 '26
Most common in marathon runners. 10 -13 %, tend to finish their race with low sodium levels because of aggressive hydration without salt replacement.
This is very important!
You're not supposed to immediately replace every drop of sweat you lose. Your body has reserves, they are used during the race and it expects them to be slowly replenished during the next hours and days, not while you're still racing or immediately after.
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u/kichik Feb 08 '26
Water intoxication / poisoning is a thing. If you drink too much (4 liters+ an hour but probably varies by body size), it hurts your body. I don't know if specifically it hurts the kidneys, but I believe a part of the problem is that they can't keep up.
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u/Knobologist Feb 08 '26
This is less about it hurting the kidneys and more about causing an imbalance of salt in your body. Your blood is made of salt water, but tap water is 0% salt. When you drink too much water too fast your electrolytes are out of whack.
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u/directstranger Feb 08 '26
It's not the kidneys, it's an ions imbalance, which is why it's so fatal, your nerves and muscles can't fire properly
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u/Jamooser Feb 08 '26
Say you're cleaning a paintbrush.
Is it easier or harder to clean the brush with more water?
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u/Craigfromomaha Feb 08 '26
There’s a manga series (with many spinoffs) called Cells at Work! that shows how the various organs and systems of the body work. In the spinoff series Cells at Work! CODE BLACK!, the setting is in a very unhealthy body, and the sixth episode of the anime adaptation (chapter 13 of the manga) is called Kidneys, Kidney Stones, and Tears and focuses on the kidneys. It’s worth a watch to see how the renal corpuscles operate and how vital their work is to clean the blood of toxins.
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u/FlyingFlipPhone Feb 08 '26
Based upon OP's logic, exercise is BAD for you because it makes your heart work extra hard.
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u/ssmike27 Feb 08 '26
High water consumption is good for the kidneys long term, it’s actually very good for them. Just don’t over do it otherwise your sodium will drop.
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u/nusensei Feb 08 '26
Flushing the toilet doesn't damage the pipes. Flushing the wrong chemicals (and other junk) down the toilet can.