Background and Aims: Serum FGF23 is known to markedly rise in patients with chronic kidney disease and has been found to be associated with dysregulated mineral metabolism and cardiovascular morbidity and mortality in these patients. It was discovered also that FGF23 rise in patients with acute kidney injury and has been suggested that its high level in those patients is associated with adverse outcomes. Many different mechanisms have been suggested for the FGF23 rise in acute kidney injury which appears to be independent of its classic regulators as serum phosphate, PTH, and vitamin D. one of these possible mechanisms is decreased renal clearance of FGF23 with impaired renal function. In this study, correlation of FGF23 with serum creatinine and other laboratory markers were studied