Very Few Know the Real Reason Why Urine Is Yellow: Here's the Explanation

Written by Henrik Rothen

Jan.08 - 2024 10:15 AM CET

Very few know the real reason why urine is yellow.

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Not everyone knows why urine is yellow. If you've ever wondered why your urine is sometimes yellow, you're not alone. The secret behind urine's yellow color is not widely known, even though the explanation has been available for some time.

But what is the real reason for this color change?

According to, which has investigated this topic, urine's color is not a direct result of the food we eat. Instead, it is a byproduct of the breakdown of red blood cells.

This process occurs in the liver, spleen, or bone marrow, where red blood cells typically break down after about 120 days.

When blood cells break down, part of them, known as hemoglobin, is destroyed. The heme group, crucial for binding oxygen to blood cells, is converted into bilirubin during the breakdown process. Bilirubin is a yellow-orange pigment that plays an important role in coloring both urine and feces.

"In the intestine, bilirubin is converted to urobilinogen by intestinal bacteria, some of which are reabsorbed, converted to urobilin, and excreted through the kidneys, coloring the urine yellow. The unabsorbed urobilinogen is converted to colored pigments, excreted with feces, and turns it brown," explains Max Salomonsson, Associate Professor of Renal Physiology at the Biomedical Institute, University of Copenhagen.

The color of urine can also serve as an indicator of our hydration level - especially during warmer periods like spring.