Explain the Urine Creatinine Test

This test measures the amount of creatinine in urine. A measurement of the serum creatinine level is often used to evaluate kidney function. Urine creatinine levels can be used as a screening test to evaluate kidney function, or can be a part of the creatinine clearance test. Creatinine, as you would know, is a breakdown product of creatine, which is an important constituent of muscle. By far, the most important source of energy inside cells are the high-energy phosphate bonds of the ATP molecule. When one of these bonds is broken, energy is released and ATP becomes ADP. Creatine phosphate represents a backup energy source for ATP because it can quickly re-convert ADP to ATP.

 The creatine molecule gradually degrades to creatinine with time. Creatinine is a waste product, that is, it cannot be used by the cells for any constructive purpose. The daily production of creatine, and subsequently creatinine, depends on the muscle mass, which fluctuates little in most normal people over long ranges of time. Creatinine is excreted from the body entirely by the kidneys. With normal kidney function, the serum (blood) creatinine level should remain constant and normal. In normal human adult, the value is relatively constant. The average value is 15 ml/ minute. Normal values are highly dependent on the age and lean body mass of the person from whom the urine is being collected from. Urine creatine (24 hour sample) values may, therefore, be quite variable and can range from 500 mg/day to 2000 mg/day.

The abnormal values of urine creatinine and creatinine clearance are often non- specific.