Creatinine

Endogenous creatinine is excreted by filtration through the glomerulus and by tubular secretion. Clinically, creatinine clearance is an acceptable measure of glomerular filtration rate but sometimes overestimates GFR. For each 50% reduction in GFR, serum creatinine approximately doubles. 

Normal Range: 0.6-1.2 mg/dL


increased in: Acute or chronic renal failure; urinary tract obstruction, nephrotoxic drugs. 

Decreased in: Reduced muscle mass, possible drug effect. 

 

Additional: In alkaline picrate method, substances other than Cr (eg, acetoacetate, acetone, b-hydroxybutyrate, a-ketoglutarate, pyruvate, glucose) may give falsely high results. Therefore, patients with diabetic ketoacidosis may have spuriously elevated Cr. Cephalosporins may spuriously increase or decrease Cr measurement. Increased bilirubin may spuriously decrease Cr.