Objectives: Kinetic glomerular filtration rate estimation may have more power and versatility than the Modification of Diet in Renal Disease or CockcroftGault formula for evaluating kidney function when plasma creatinine fluctuates rapidly. After kidney donation, glomerular filtration rate rapidly fluctuates in otherwise healthy patients. We compared 3 formulas for estimating glomerular filtration rate: kinetic, Modification of Diet in Renal Disease, and Cockcroft-Gault, for determining stages of acute kidney injury early after kidney donation. Materials and Methods: In 42 living kidney donors, we measured serum creatinine, cystatin C, neutrophil gelatinase-associated lipocalin, and glomerular filtration rates before uninephrectomy and 3 days afterward. To estimate glomerular filtration rate, we used Cockcroft-Gault, Modification of Diet in Renal Disease, and kinetic equations. We sought the most accurate formula for staging acute kidney injury according to the risk, injury, failure, loss, and end-stage criteria. Results: The kinetic glomerular filtration rate model found more cases of stage 3 acute kidney injury than did the Modification of Diet in Renal Disease or Cockcroft-Gault formula. Receiver operating characteristic curves showed that the kinetic glomerular filtration rate model had more sensitivity and specificity than the Cockroft-Gault formula for discriminating among risk, injury, failure, loss, and end-stage criteria stages of acute kidney injury, based on serum creatinine changes. On day 2 after donation, a more sensitive marker with a shorter half-life (serum neutrophil gelatinase-associated lipocalin) was more significantly correlated with kinetic glomerular filtration rate estimation. Conclusions: The kinetic glomerular filtration rate model was able to discriminate stages of acute kidney injury early after kidney donation according to risk, injury, failure, loss, and end-stage criteria better than the Modification of Diet in Renal Disease or CockcroftGault formulas. The kinetic model detected failurestage acute kidney injury ≥ 1 to 2 days earlier than the MDRD formula, CG formula detected no failure.