A yellow pigment produced from the breakdown of red blood cells, processed by the liver and excreted in bile. Elevated levels cause jaundice and indicate liver disease or excessive red cell destruction.
From Latin 'bilis' (bile) + 'ruber' (red), literally meaning 'red bile,' named in 1864 for its reddish color before oxidation to yellow. The name reflects its origin from red blood cell breakdown and presence in bile.
Bilirubin is why bruises turn yellow as they heal - it's the same pigment! Your body breaks down 250 billion red blood cells daily, producing about 250mg of bilirubin that must be processed by the liver or you'd turn permanently yellow.
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