Which laboratory test is most indicative of kidney function?

Serum creatinine is considered the most indicative laboratory test for kidney function because it directly reflects the kidneys' ability to excrete creatinine, a waste product of muscle metabolism. Normally, the kidneys filter creatinine from the bloodstream, and when kidney function declines, serum creatinine levels rise.

Unlike blood urea nitrogen (BUN), which can be influenced by various factors such as protein intake and dehydration, serum creatinine provides a more specific assessment of renal function. Additionally, while the electrolyte panel can give information about the balance of electrolytes, it does not specifically indicate kidney filtering capability.

The glomerular filtration rate (GFR) is indeed a crucial measure of kidney function; however, it is often estimated using serum creatinine levels in conjunction with other factors, such as age, sex, and race. Therefore, while GFR is important and provides a comprehensive view of kidney function, the serum creatinine test is the standard and most direct assessment of how well the kidneys are filtering waste from the blood.