What is the primary diagnostic test for assessing kidney function?

Serum creatinine levels are considered the primary diagnostic test for assessing kidney function because creatinine is a waste product generated from muscle metabolism, and its levels in the blood are relatively stable. The kidneys typically filter creatinine from the blood, and elevated serum creatinine levels can indicate that the kidneys are not functioning properly.

This test is particularly reliable because creatinine is produced at a constant rate and is not significantly influenced by diet or hydration status, making it an effective marker for glomerular filtration rate (GFR). An increase in serum creatinine levels often correlates directly with a decrease in kidney function, providing healthcare professionals with critical information regarding renal health.

While blood urea nitrogen (BUN) levels, electrolyte levels, and urinalysis can also provide useful information about kidney function and overall health, BUN is influenced by protein intake and hydration status, and urinalysis primarily assesses filtration and secretion capabilities rather than direct kidney function. Electrolyte levels can indicate imbalances due to kidney dysfunction but are not specific for assessing kidney function on their own.