system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When I pee, am I peeing out the water I drank recently, or the water I drank yesterday to make room for the new water?
gpt
When you drink water, it eventually becomes part of your blood. Your kidney regulates your blood pressure by drawing out water from the blood, which gets excreted as urine. So it's not really possible to differentiate water you drank now from water you drank earlier or even water your body produced.