Key Takeaways

Have you ever wondered why yourpee is yellow? Until recently, not even scientists who study the human body had a clear answer to the urine color conundrum.

“This enzyme discovery finally unravels the mystery behind urine’s yellow color,”Brantley Hall, PhD, lead author of the study and assistant professor at the University of Maryland, said in anews release. “It’s remarkable that an everyday biological phenomenon went unexplained for so long, and our team is excited to be able to explain it.”

Researchers have long known that pee’s unique color is down to urobilin, Hall told Verywell. However, no one had been able to pinpoint exactly what created that chemical in our bodies.

Other than finally solving the pee pigment mystery, the researchers think the findings could also be applied to future studies of gut health to help us better understand conditions like jaundice and inflammatory bowel disease.

“Now that we’ve identified this enzyme, we can start investigating how the bacteria in our gut impact circulatingbilirubinlevels and related health conditions like jaundice,”Xiaofang Jiang, PhD, a study co-author and National Institutes of Health investigator, said in apress release. “This discovery lays the foundation for understanding the gut-liver axis.”

What the Weird Color or Smell of Your Urine May Mean

What Makes Pee Yellow?

Urine is yellow because of a chemical called urobilin which comes from the enzyme bilirubin, David Shusterman, MD, a board-certified urologist and founder of NY Urology, told Verywell. When your body breaks down old red blood cells, it makes a yellow chemical substance called bilirubin.

Your liver uses this bilirubin to makebile, a fluid that helps digest food, Shusterman said. Some of that bile goes directly to your intestines, and the rest is stored in your gallbladder.

Good bacteria in your intestines break down some of the bilirubin in your bile intourobilinogen, which becomes urobilin. Some of this substance comes out in poop, some goes back to your liver, and a bit of it leaves your body through urine. That’s why urine is yellow.

When red blood cells are at the end of their life, they’re broken down, which creates bilirubin,Jamin Brahmbhatt, MD, a board-certified urologist at Orlando Health, told Verywell.

According to Hall, a key reason the researchers were able to find this enzyme was that they could combine studying gut bacteria genes with lab experiments.

“Until recently, bacteria in the gut have been very difficult to study, but with modern advances in our ability to sequence genomes and perform experiments on gut bacteria, we have started to be able to look at what different bacteria are doing in our guts,” Hall said.

Dark Urine: Symptoms, Causes, and Treatment

Why Isn’t PeeAlwaysYellow?

The color of your urine can actually vary depending on different factors, including howhydrated you areand certain foods that you eat,Gauthami Churukanti, MD, a urologist at Stony Brook Medicine in New York, told Verywell.

For example, if you are well-hydrated, your urine tends to be “pale and lighter in color, almost like water itself,” Churukanti said. On the other hand, if you are dehydrated, you’ll have very concentrated urine that’s a darker yellow color.

The reason hydration plays a major role in urine coloration is that when you are well-hydrated, your body has more water available to mix with the substances in your urine, according to Hall. The water essentially “dilutes the urobilin.” Dilution makes the concentration of yellow pigments, like urobilin, lower, resulting in a lighter and pale color in your urine.

Churukanti said other factors that can influence the color of your pee include:

Should You Be Concerned About Blood in Your Urine?

What Your Urine Color Can Tell You

Although urine color varies from person to person, generally speaking, it should be yellow, Brahmbhatt said.

“Lemonade yellow is usually a good sign. It means you’re probably drinking enough water,” said Brahmbhatt. However, if your pee is getting darker, like apple juice, it could be a sign that you need to drink more water.

If your urine looks green or orange, it’s usually from the foods you are eating or medications you are taking, said Brahmbhatt. On the other hand, if your urine is turning brown or red, it could be a sign of something more serious.

“Blood in the urine—either you see it or it’s found on labs—is a serious matter that requires a workup. Don’t ignore it!” Brahmbhatt said.

What This Means For YouAn enzyme called urobilin makes pee yellow. While urine color can vary from person to person based on diet, hydration, medications, and health conditions, healthy urine is generally yellow. If you notice any sudden changes or consistently notice have odd-colored pee, it’s best to check in with your healthcare provider.

What This Means For You

An enzyme called urobilin makes pee yellow. While urine color can vary from person to person based on diet, hydration, medications, and health conditions, healthy urine is generally yellow. If you notice any sudden changes or consistently notice have odd-colored pee, it’s best to check in with your healthcare provider.

What Does It Mean If Your Urine Is Orange?

5 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Hall B, Levy S, Dufault-Thompson K, et al.BilR is a gut microbial enzyme that reduces bilirubin to urobilinogen.Nat Microbiol. 2024;9(1):173-184. doi:10.1038/s41564-023-01549-xUniversity of Maryland.What makes urine yellow? UMD scientists discover the enzyme responsible.MedlinePlus.Urobilinogen in urine.Belasco R, Edwards T, Munoz AJ, Rayo V, Buono MJ.The effect of hydration on urine color objectively evaluated in CIE Lab* color space.Front Nutr.2020;7:576974. doi:10.3389/fnut.2020.576974Urology Care Foundation.The meaning behind the color of urine.

5 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Hall B, Levy S, Dufault-Thompson K, et al.BilR is a gut microbial enzyme that reduces bilirubin to urobilinogen.Nat Microbiol. 2024;9(1):173-184. doi:10.1038/s41564-023-01549-xUniversity of Maryland.What makes urine yellow? UMD scientists discover the enzyme responsible.MedlinePlus.Urobilinogen in urine.Belasco R, Edwards T, Munoz AJ, Rayo V, Buono MJ.The effect of hydration on urine color objectively evaluated in CIE Lab* color space.Front Nutr.2020;7:576974. doi:10.3389/fnut.2020.576974Urology Care Foundation.The meaning behind the color of urine.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Hall B, Levy S, Dufault-Thompson K, et al.BilR is a gut microbial enzyme that reduces bilirubin to urobilinogen.Nat Microbiol. 2024;9(1):173-184. doi:10.1038/s41564-023-01549-xUniversity of Maryland.What makes urine yellow? UMD scientists discover the enzyme responsible.MedlinePlus.Urobilinogen in urine.Belasco R, Edwards T, Munoz AJ, Rayo V, Buono MJ.The effect of hydration on urine color objectively evaluated in CIE Lab* color space.Front Nutr.2020;7:576974. doi:10.3389/fnut.2020.576974Urology Care Foundation.The meaning behind the color of urine.

Hall B, Levy S, Dufault-Thompson K, et al.BilR is a gut microbial enzyme that reduces bilirubin to urobilinogen.Nat Microbiol. 2024;9(1):173-184. doi:10.1038/s41564-023-01549-x

University of Maryland.What makes urine yellow? UMD scientists discover the enzyme responsible.

MedlinePlus.Urobilinogen in urine.

Belasco R, Edwards T, Munoz AJ, Rayo V, Buono MJ.The effect of hydration on urine color objectively evaluated in CIE Lab* color space.Front Nutr.2020;7:576974. doi:10.3389/fnut.2020.576974

Urology Care Foundation.The meaning behind the color of urine.

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