Science explains why coffee makes you pee so damn much

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cup of coffee on brown tile table with coffee beans
Photo: REDA&CO / Contributor (Getty Images)

Oh, coffee, the bane of morning meetings everywhere. It’s a necessary evil; the coffee wakes you up, but in the meantime, it turns you into a walking pee factory, turning any office interactions into an uncomfortable squirmfest. Now, it’s a given that the culprit at hand is caffeine, but how does this whole process actually work? Takeout contributor Julie Kendrick, writing for HuffPost, took a look into this, and it turns out our bodies are a marvel of biological engineering.

The journey starts in your stomach. It does depend on how much food you’ve eaten: if you’re full, the coffee can take over an hour to get to your intestines. Since liquids digest so much faster than solid food, your body starts processing coffee on an empty stomach quickly.


Here’s where the pee talk comes in, according to Lisa Anderson, associate professor of integrative biology and physiology at the University of Minnesota: “Once the fluid has made its way to the bladder, sensors there begin to notice that the bladder is filling up. That sets off signals to the micturition center in your brain stem, which sits by other centers that tell you things like when you’re thirsty, hungry or need to vomit.”

“Micturition” is the fun science word for pee. The world is such a marvelous place.


The caffeine in coffee gets pee moving faster because caffeine gives your detrusor muscle, a smooth muscle in your bladder’s wall, an extra boost of stimulation. Because your brain is already aware of the liquid in your bladder, in concert with the caffeine adding extra stimulation to the detrusor muscle, you’re going to start feeling those ants in your pants pretty fast.

Here’s a fun little tidbit: Anderson said that men “can hold more fluid in their bladders, and hold it for longer.”


Caffeine, as some of you know, is a diuretic, too, which means that your kidneys are pulling more water out of your system than just the amount you drank in that cup of coffee. Once you hit around 400 milligrams of caffeine, your body’s natural fluid balance starts being affected. Those 400 milligrams are roughly the amount you get in four cups of brewed coffee, which is also the maximum daily recommended amount of caffeine. Make sure you drink your water, everybody!

Now, if you feel like you’re going to the bathroom way too often, it doesn’t hurt to change your caffeine habits slowly by tapering off your coffee consumption a bit. But if your pee breaks are starting to disrupt your life, don’t be afraid to ask your doctor about these things, just in case.