Mind & Body

Why Is Pee a Shade of Yellow, No Matter What You Eat or Drink?

Bathroom subjects don't get enough credit. They're undeservedly taboo topics, and undeniably important. We're not talking about potty mouths or fart jokes, but rather the science of what you're flushing down the toilet. Urine, for one, can give you key clues about the state of your health. Let's tackle the tinkle and talk pee. C'mon, we're all adults here.

And It Was All Yellow

Surely it goes without saying that urine is critical for helping remove waste from your body. Thanks, pee! But the color begs another question: Why is urine almost always a shade of yellow, no matter what you eat or drink? The culprit is a chemical called urobilin or urochrome.

Here's the whole story: Your body has a massive amount of red blood cells, but they don't last very long before needing to be washed out of your system. Even after they've passed their expiration dates, red blood cells contain iron. White blood cells gobble up the iron to keep it in your body and dispose of the ex-red blood cell wrapper, called bilirubin. A gut bacteria called urobilinogen intercepts this bilirubin in your bloodstream and escorts it to one of two exits (you shouldn't need an explainer there).

On the pee route, the bilirubin is sent to the kidneys, which suck out valuable nutrients and transform the stuff into a molecule that happens to be yellow: urobilin. It's then sent on its way to the toilet bowl. The amount of water in your body can dilute this urobilin, making your pee any yellow-y shade between crystal clear and deep amber.

Pee the Rainbow

The shade of sunshine that you excrete as liquid waste into the toilet is a message. Different colors of pee mean different things about your health. Let's start with the yellows:

  • Totally clear: You've been drinking a ton of water, haven't you? You could do with a little less hydration.
  • Pale straw color: Ding ding ding! You win the urine award! A very light, nearly clear yellow pee means you're healthy and well-hydrated.
  • Transparent yellow: Yup, you still good.
  • Deeper yellow: You're normal, but you should probably think about drinking some water soon.
  • Amber or honey-colored: Thirsty? You're dehydrated, pal. Drink some water, stat.
  • Neon yellow: This could be caused by excess riboflavin, which means you probably just popped a multivitamin.

Nothing on the yellow pee scale is too alarming; it's basically a litmus test for hydration. While some variety of yellow is probably what you're used to seeing every day, other colors are possible. Sounds fun, but it's probably not; most of these instances require a call to your doctor. Better safe than sorry.

  • Brown-ish syrup color: You're either severely dehydrated, or something else is wrong, like liver disease. Drink lots of water and see if the problem doesn't clear itself out. If brownish pee persists, call a doctor.
  • Pink or reddish: You may have just eaten a bunch of beets, blueberries, or rhubarb. But, perhaps you have blood in your urine. Blood could mean nothing, but it's definitely something to contact your doctor about right away. It could be a sign of kidney disease, urinary tract infection, prostate problems, tumors, or something else.
  • Orange: This could either mean you're really dehydrated, or you have a liver or bile duct condition. You guessed it — call your doctor.
  • Blue or green: Believe it or not, certain rare genetic diseases can give you some interesting hues of urine. It could also be from food dye, medication, or a urinary tract infection. Ring the doc.
  • Fizzy or foamy: Okay, this one isn't a color, but fizziness can happen from time to time in the loo. If it's occasional, it's probably a harmless hydraulic effect. If foaming is persistent, it could be kidney problems or excess protein in your diet. Talk to your doctor if you're concerned.

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For more nagging questions about human biology, check out "Ask a Science Teacher: 250 Answers to Questions You've Always Had About How Everyday Stuff Really Works" by Larry Scheckel. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Joanie Faletto October 10, 2017

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