Diagnosis of Acute Tubular Necrosis Differentiation from prerenal azotemia, based mainly on laboratory findings and, in the case of blood or fluid loss, response to volume expansion Acute tubular necrosis is suspected when serum creatinine rises ≥ 0.3 mg / dL / day (26.5 micromol / liter [μmol / L]) above baseline or a 1.5 - to 2.0-fold increase in serum creatinine from baseline after an apparent trigger (eg, hypotensive event, exposure to a nephrotoxin); the rise in creatinine may occur 1 to 2 days after certain exposures (eg, IV radiocontrast) but be more delayed after exposure to other nephrotoxins (eg, aminoglycosides).