How long does it take for water to get from your mouth to your bladder?
March 26, 2010 9:34 AM   Subscribe

How long between drinking water and having to pee?
posted by DMelanogaster to Health & Fitness (16 answers total) 3 users marked this as a favorite
Google consensus says 45 mins to an hour.
posted by royalsong at 9:37 AM on March 26, 2010

That corroborates my personal (ahem) research.
posted by The Winsome Parker Lewis at 9:38 AM on March 26, 2010

It seems like about ten minutes to me. Which is obviously Wrong.
posted by DMelanogaster at 9:39 AM on March 26, 2010

It depends on how much water you drink and what else you have ingested and how hot it is and any number of other factors.
posted by mareli at 9:45 AM on March 26, 2010 [1 favorite]

Yeah, it really depends. One time I had to do a ("random") drug test first thing in the morning at work. But, I'd just swam for an hour, and had not rehydrated. So I downed two quarts of water (!) and.....waited. It was still an hour later before I finally peed.
posted by notsnot at 9:49 AM on March 26, 2010

This is not really an easily answerable question. It depends on how much volume was already in your bladder when you had the drink, your insensible fluid losses at the time due to sweating and breathing, your circulating blood volume, your electrolyte balance, how good your kidney and heart function is, and how rapidly you absorb the water from your gut.
posted by drpynchon at 9:51 AM on March 26, 2010

I should add that the half-life of water (if for example you were to drink some form of labeled water) is 7-14 days. In other words, about 10 days after you had that drink, half of that cup is still floating around in you. The kidneys and your urination frequency have no direct response to your fluid intake. They respond sort of reflexively to the blood flow they see.
posted by drpynchon at 9:56 AM on March 26, 2010 [1 favorite]

I think he's asking for an average.

For me it seems that if I drink a huge amount really quickly, I have to go to the bathroom much sooner. If I drink a few sips all day long, I can go all day long without using the restroom.
posted by lakerk at 10:02 AM on March 26, 2010

It also depends upon your age, and whether or not you have had a baby.
posted by MexicanYenta at 10:13 AM on March 26, 2010

You could really only get a standardized answer by being hydrated to a standardized degree (which isn't really possible, but might involve eating and drinking standardized food and beverage, doing a standardized amount of moving around and activity, in a room with standardized humidity, for a day or two). Then maybe you could completely empty your bladder by peeing, and then drink a bunch of water and time your response. And it would still only be accurate to you, under those circumstances, not other people or other circumstances.

The process works like this: First, the water has to be absorbed into your bloodstream from your stomach and intestines (which can absorb about 1/4 Liter about every 15 minutes). Then, assuming you were already at optimal hydration levels, your kidneys would notice that there's more blood coming to them (because of the greater volume of fluid in the blood). Your kidneys are always producing some urine because they need to get rid of wastes from your blood, but when they notice the extra blood volume they will decide to get rid of the extra water at the same time. That means they'll produce more dilute urine, so a greater volume of liquid (urine) would go to your bladder. Depending on the size of your bladder and how reactive it is, eventually the increasing amounts of urine being stored there will trigger a need to urinate.

So if you were already dehydrated (whether from exercise or from not having anything to drink for a while or whatever), your kidneys won't ramp up urine volume production because they'll just think "oh good, there's finally enough fluid in the blood again." Or if you ate a ton of salty food, the kidneys might say "we should keep some of this water around, to help dilute all the salt!" In those cases it could take longer before you have to pee.

If, like lakerk, you drink sips all day long, your blood volume won't go up enough to make your kidneys take notice. Rather than all those sips building up in your blood to noticeable levels, you'll lose most of the extra fluid by breathing and sweating. But of course you'll still have to pee eventually, because your body has to get rid of more than just water through the urine. In fact, 500mL is about the least amount you can pee each day and still get rid of those other waste products from your blood.

On the other hand, if you happen to have a particularly small or reactive bladder, it might make you feel like you have to pee when there is less urine in there compared to somebody else. So maybe you'd sense the need to urinate when only 250 mL of urine has been made, compared to someone who could wait until 350 mL of urine shows up before getting uncomfortable. Or maybe you just drank a huge amount of water and are wearing too-tight pants, in which case the sense of pressure in your abdomen might lead you to feel the urge to pee sooner, even though most of the water hasn't hit your bloodstream yet. That's a lot like if you're pregnant, and the baby is squishing your bladder so much that you have to pee all the time.

Anyway, there's a lot that goes into it. The anecdotal 45-60 minutes you're getting above sounds about right, though.
posted by vytae at 10:32 AM on March 26, 2010 [8 favorites]

If I'm at an airport it's generally about five minutes after I've boarded. Otherwise? it's about 30 minutes unless it's a really hot day.
posted by FlamingBore at 10:57 AM on March 26, 2010

If the question is "How long does it take after drinking water before it's time to urinate," well, that's going to depend on a variety of factors, chief of which are how well hydrated you were to begin with and how full your bladder is already. If you were parched, drinking something might not cause you to urinate much at all and not for quite some time. If you're in the middle of a kegger, it could be minutes at best. What happens is not that the water "passes through" more quickly but that, in response to the addition of more water, the body causes the kidneys to get to work.

But if the question is "How long does it take for a particular molecule of water to pass from my mouth to my kidneys," the answer is "An indefinite period." Think of it as an inventory system. While it isn't exactly FIFO, the odds are pretty good that the next liter you pee won't have much of the last liter of water you drank in it. As mentioned above, the half-life of water is days to weeks, but the body actually uses water in metabolic processes in addition to just using it as a solvent. Depending on how it gets used, a given atom or molecule could stay with you for years.
posted by valkyryn at 11:16 AM on March 26, 2010

My 4-year-old son can stop drinking water at 6:30pm, pee at 7:30pm, get woken up at 10pm to pee, get woken up at 11:30pm to pee again, and still wet his bed at around 5am or so. The journey is a personal one, and so is the duration, I guess.

and my son will be thrilled to read this comment someday. the internet never forgets!
posted by davejay at 2:36 PM on March 26, 2010

Oh, and fwiw, I've had something to drink at 9:30am, then gone until 6pm without having to pee. Again, personal journey.
posted by davejay at 2:37 PM on March 26, 2010

My anecdotes:
If I go out to lunch, I tend to drink a lot of water with the meal. I have to pee when I get back to the office, but then about a half hour later, I REALLY have to pee. Sucks if I'm in a training class or some restricted area after lunch.

While visiting India, I just couldn't use those hole-in-the-floor bathrooms. I spent one entire day without having to pee at all, even though I continued to drink water throughout the day. I guess I drank in small enough portions to not raise my blood level (or whatever). I did sweat a lot that day.
posted by CathyG at 3:17 PM on March 26, 2010

I was thinking about this just the other day.

I've been dieting a bit, watching my intake of food, watching calories and logging my meals.
I stopped drinking regular soda and drinking a whole lot more water. I have a 44oz cup from the gas station that I fill at lunch time, and drain it twice before 5pm. I brought some lemon to work with me the other day and found that I had finished almost 3 and a half cups. Something about the lemon made the water taste better, or more appetizing anyway. I had to pee- A LOT!! Which got me thinking about this. Anyway, thanks for asking the question.
posted by TuxHeDoh at 8:21 PM on March 26, 2010

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