How long does it take fluid to reach the bladder?

Answer 1

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 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.

Answer 2

Fluid starts going to the bladder in 30 minutes.

Answer 3

up to 60 minutes