Serum Creatinine Test

Creatinine is a waste product generated by normal muscle metabolism at a fairly constant rate, and because it's filtered out of the blood almost entirely by the kidneys, measuring its level in your blood is one of the most reliable and widely used indicators of kidney function.

When kidney function declines, the kidneys become less efficient at filtering creatinine out of the blood, causing it to build up and creatinine levels to rise — often before a person notices any symptoms of kidney trouble at all.

Because creatinine production is related to muscle mass, normal levels differ somewhat between men and women, and this needs to be factored in when interpreting results, particularly for the calculated eGFR value that's typically derived from creatinine.

This test is simple, requires only a standard blood draw, and is one of the most commonly ordered tests in both routine checkups and hospital settings.