Alcohol tends to make simple things suddenly really complicated. You might think that the answer is obvious. Beer goes in, Pee comes out. Beer is mostly water, so why wouldn’t it make you pee? The answer is a bit more complicated than that, and it has to do not just with beer, but any drink that has the active ingredient, ethanol, also known as ethyl alcohol. You probably know that alcohol messes with all sorts of brain functions, just first-hand, probably. It does this by making it harder for your neurons to communicate with each other, but it also affects your endocrine system, that network of glands that secretes the hormones your body needs to keep your heart beating and your cells metabolizing. In this case, alcohol interferes with a specific hormone secreted from your pituitary gland called Vasopressin, sometimes called anti-diuretic hormone.

One of the major roles Vasopressin plays in the body is to help your body retain water. It sends signals to your kidneys to keep your body hydrated by maintaining just the right balance of water and mineral salts in your blood. But while the alcohol is messing with your brain, it’s also messing with your pituitary gland and actually turns off the production of Vasopressin. Without those orders being sent to your kidneys to retain a certain amount of water, they just start letting all the water in your system through, sending it straight to your bladder. The more alcohol you ingest, the less Vasopressin you produce, the more water you lose. That is why after a couple of drinks, you’ll notice that your urine becomes lighter in color, and if you’ve had way too much, eventually comes out clear. At that point, you’re essentially peeing out nothing but water. When you see that, you know that you’ve not only had too much, but you’re in for an experience the next day because dehydration is one of the main causes of hangover.