Which substance is commonly tested to assess liver function?

Bilirubin is a key substance commonly tested to assess liver function because it is a product of the breakdown of red blood cells. The liver plays a crucial role in processing bilirubin, converting it from its unconjugated form (which is not water-soluble and can be harmful if it accumulates in the blood) to its conjugated form (which is water-soluble and can be excreted in bile). Elevated levels of bilirubin in the blood can indicate liver dysfunction, biliary obstruction, or hemolysis, making it a vital marker in evaluating liver health.

In contrast, glucose levels are primarily related to carbohydrate metabolism and insulin function rather than direct liver performance. Urea is a product of protein metabolism, indicating kidney function more than liver function. Similarly, creatinine is used to assess renal function, as it is a waste product filtered by the kidneys. Thus, bilirubin is specifically relevant in assessing liver function due to its direct connection to the organ's ability to process and excrete it properly.