Drink, then pee.
Broken kidneys?

The full narration of the video.

Peeing right after you drink doesn't mean your kidneys are broken. It means they're doing their job. You gulp down a big glass of water, and soon you're hunting for a bathroom. Others drink two glasses and sit tight, while one sends you running. So you start to worry. Where does that water actually go? Let's follow it.

First it reaches the gut and gets absorbed into the blood. Your blood becomes just a little more watery. That blood flows through the kidneys. In a single day, your two kidneys filter about a hundred and fifty liters. Enough to fill a bathtub. Yet you only pee out one or two liters a day. The other ninety-nine percent goes right back into the blood.

Think of the kidney as a big basin at home. All the household water passes through it every day. Along its edge, a row of return gates sends water back into the house. Whatever doesn't go back runs into a small bucket and gets tipped out. That bucket is your urine. So who decides how wide those gates open? The brain. A small spot at its base keeps watch on whether your blood is thick or thin. When the blood turns thin, it sends out less of a certain signal. The last few gates swing partly shut. Less water goes back, so more flows into the bucket. The urine comes out plentiful and pale.

Flip it around: sweat a lot and drink little, and the blood thickens. The signal ramps up, and those gates swing wide open. Water is saved, and you pee less and darker. That signal has a real name: antidiuretic hormone. The name says what it does: it stops you peeing too much. You can't see it, but you can see its work. Urine as clear as water means it's easing off. Deep yellow means it's working hard to save water.

Here's an odd thing. When thirsty people drink, their blood hasn't even had time to thin out. Yet within about fifteen minutes, the hormone has already dropped. The moment water touches the mouth and throat, they tip off the brain. So needing to pee after drinking is your kidneys keeping pace with you: drink more, they let more go; drink less, they hold on.

What deserves attention is peeing a lot without drinking much, and being very thirsty. Getting up again and again at night, or passing more than two and a half liters a day. Then it's time to see a doctor and get your urine and blood sugar checked. Tomorrow morning, drink a big glass of water on an empty stomach. Time your first bathroom trip, and come back and tell us how many minutes it took.