Medical Health Encyclopedia

Creatinine - urine

How the test will feel:

The test involves only normal urination, and there is no discomfort.

Why the test is performed:

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A measurement of the serum creatinine level is used to evaluate kidney function. Urine creatinine levels can be used as a screening test to evaluate kidney function, or as part of the creatinine clearance test.

Creatinine is a breakdown product of creatine, which is an important part of muscle. By far, the most important source of energy inside cells is the ATP molecule, with its high-energy phosphate bonds.

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 back to ATP.

Over time, the creatine molecule gradually degrades to creatinine. Creatinine is a waste product, that is, it cannot be used by cells for any constructive purpose. The daily production of creatine, and subsequently creatinine, depends on muscle mass, which fluctuates little in most normal people over long periods 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.

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