The Science of Why Your Pee is a Yellow Color

The Science of Why Your Pee is a Yellow Color

Your kidneys & liver are where the magic happens. Pee is made up of water and dissolved waste material from what you have been drinking and eating. It also includes material the body wants to eliminate, like dead blood cells and other things.

Urochrome is a yellow pigment that comes from the processing of dead blood cells in the liver. The liver protects your body from harmful substances by screening out the stuff in your blood that flows directly from your stomach and intestines.

Urobilin are the breakdown products of the bile pigment bilirubin, which itself is the breakdown product of the heme part of the hemeglobin from old blood cells. Most bilirubin is partly broken down in the liver before making its way through your intestines and out in your poop. Some remains in your bloodstream and is extracted by the kidneys.

The kidneys act as a filter for your blood, allowing water, sugars, vitamins, amino acids and other vital substances back into the bloodstream... all while eliminating excess water, salts and minerals, as well as urea from protein digestion, uric acid, creatinine from muscle breakdown, hormone waste and toxins. The remaining bilirubin is extracted by the kidneys, where converted it gives urine that familiar yellow color.

Urochrome and the degradation products of bilirubin and urobilin, make our pee yellow.


Are You Peeing Bling?

Gold Pee


Some early Alchemists believed that the yellow-gold color of pee might be from actual gold and employed all sorts of experiments with it trying to derive gold from pee. As you might have guessed, there wasn't "Gold in them thar hills!" But, one German merchant and amateur-alchemist, Henning Brand did find phosphorus while performing an experiment with pee hoping for gold... Phosphorus is commonly used in safety matches and pyrotechnics.


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Showing 1 - 7 of 7 Comments
Interesting article.
Several hundred years ago urine was used in some gunpowder manufacture due to the useful phosphorus content.
interesting article. i love this kind of stuff.

i have also always wondered why bird poop is white. i think i was told that its because they don't have separate - um - openings... so the pee and poop combine and it causes it to be white, unless they just ate mulberries!
i also wonder why some foods affect urine colour and others don't. beets make it red (scary when changing babies' diapers!) and asparagus makes it green, but i can't think of any others. oh, and on House they did a thing where they talked about how viagara makes it blue.
i love the image at the top. :)
Darius, always entertaining - it occurs to me that summer would be an excellent time to mention that you can gauge your current dehydration levels through shades of yellow at the urinal. Dark near-orange = bad, mostly clear = good.
What about when pee isn't the color it's supposed to be? What causes GREEN pee and clear pee and things like that?
one cause of green pee is asparagus (see above). clear pee means you're drinking lots and lots of water (good).

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