Assessment of elevated creatinine

Serum creatinine concentration is maintained by the balance between its generation, mostly in skeletal muscle, and its excretion by the kidneys. Because creatinine is generated in a steady manner and can be measured very simply from blood samples, it has become a useful test to estimate glomerular filtration rate (GFR), a measure of kidney function.

Serum creatinine levels are affected by factors that influence its generation, glomerular filtration, and tubular secretion. There is considerable variation in the excretion of creatinine based on individual patient factors and the time and method of testing. In addition, the choice of assay affects the measurement obtained.

The usual reference range of serum creatinine is:

• 60 to 110 micromol/L (0.7 to 1.2 mg/dL) for men

• 45 to 90 micromol/L (0.5 to 1.0 mg/dL) for women.

Acute kidney injury can be defined by changes in serum creatinine. Estimated GFR (eGFR) equations, based on serum creatinine, are generally used to stage chronic kidney disease (CKD).