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How worried should you be when your urine isn't yellow, but instead it's green, red, or even black?

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You’ve probably noticed that your urine changes color slightly day to day, usually depending on how much water you’ve been drinking.

But have you ever looked down and seen like a more surprising color in the toilet? Like red? Or green?

Yeah. Green pee is a thing. So is blue, purple, orange, and even black. Sometimes a weird color is a sign that something is wrong with you. But other times, it’s just evidence that you ate a certain food or medicine.

So, let’s go through the rainbow of potential pee colors... starting out with yellow, because that’s the normal one. The yellow color of urine comes from urochrome, which is one of the waste products that your body makes when it breaks down red blood cells. The precise shade of yellow depends on how hydrated you are.

If your body is conserving water, your pee will be more concentrated and have more urochrome in it, so it can end up a darker color. If it’s really dark, like basically brown, that can be a sign of a liver or kidney issue. But lots of medications can also darken your urine, like antibiotics and antimalarial drugs.

Or it could just mean that you have eaten a bunch of fava beans, aloe, or rhubarb. If you see like super neon yellow, that is not from urochrome. That’s either because you’re hallucinating or something, or because you have consumed more riboflavin, or vitamin B2, than your body can use, and you’re now just peeing it out.

An orange tint can come from eating a lot of food rich in beta-carotene, like carrots and sweet potatoes, or from certain medications, like the blood thinner warfarin. One of the brightest orange colors comes from a drug that treats the pain associated with UTIs.

If your urine is red, your first thought is probably blood, and you might be right. Blood could come from your kidney, bladder, or urinary tract because of an injury, infection, or other problem, and give your pee a pink or red tinge. So... not good.

But blood isn’t always the culprit. In beeturia, red pee comes from eating beets. Some people absorb more of the natural red pigments in beets in their intestines, and the extra red comes out in their urine.

Green urine, on the other hand, can sometimes come from an infection with a type of bacteria, called Pseudomonas, that produces green pigments. But it’s usually a side effect of medication. One drug that can make your pee look like Ecto Cooler is propofol, a common anesthetic used during surgery. When the drug is broken down in your liver, one of the products happens to be green, and it comes out in your urine.

Strangely, propofol can also turn pee white or pink. Biologists aren’t entirely sure how that works, but they think the pink urine happens because propofol can make your body produce more uric acid, which can turn urine pink.

Another drug that can make your urine green is methylene blue, which is used as a medical dye and to treat certain blood disorders. As you can probably guess, methylene blue is... blue. And when it combines with the yellow urochrome, your pee can come out a lovely shade of St. Paddy’s day green.

Because of your natural urochrome, having truly blue pee is more rare. But it does happen in people who have a genetic defect that prevents them from absorbing the amino acid tryptophan. Since this disease is often spotted early in life, it’s known as blue diaper syndrome.

Gut bacteria break down the extra tryptophan the baby can’t absorb, and eventually it gets converted into a molecule called indican. When indican hits the air, it turns into indigo dye, and voila, a blue diaper.

OK, so there is no such thing as truly purple urine, but there is totally a thing called purple urine bag syndrome, which can happen to some people if they have a UTI and are using a catheter.

The violet color comes from certain bacteria in the urinary tract, which make enzymes that break down molecules in urine into indigo, which is blueish, and indirubin, which is red. Mix the two together and you get purple. The pee isn’t purple when it comes out because the chemical reactions to make the colors need to sit at a high pH for a while, so in an alkaline, or basic, environment. People with UTIs usually have this type of alkaline urine, and the bag provides the perfect environment to create an impressive shade of dark violet.

Now if those colors aren’t weird enough, urine can also go beyond the rainbow, and be white or black. By white, I mean milky, so the urine isn’t transparent anymore. There are lots of things that can cause it, but one possibility is an out-of-control UTI that’s literally white from pus. Ewweeea!

More rarely, pee can be white because lymph fluid has leaked into the urinary system. This condition is called chyluria, and it is usually because of a parasitic worm infection.

Now black urine can happen for a lot of reasons, including some of the same ways urine gets to be red. But in alkaptonuria, or black urine disease, people don’t have enough of an enzyme that helps break down certain amino acids. That leads to a build-up of homogentisic acid, which comes out in urine and turns black in the presence of air. But the Darth Vader urine isn’t the only problem here. The acid also builds up in tissues like cartilage, staining and damaging them.

Most of the time, though, your urine is going to be plain ol’ pale yellow. Even if you see orange or green after taking some meds, it’s probably nothing to worry about. But an abnormal color is often the first clue for doctors that there might be a problem, so there's no harm in checking for a more unusual hue in the toilet bowl. And if you do see something weird, maybe talk to a doctor.

Thanks for watching this episode of SciShow. For more on the colors of excrement, check out our video where I explain why your poop might be green. Cuz that’s apparently what we’re up to here, at SciShow.