AIM: To evaluate the role of the C-13-methacetin breath test (C-13-MBT) in the assessment of acute liver injury in a rat model. METHODS: Acute liver injury in rats was induced by a single intraperitoneal injection of D-galactosamine (D-GalN). Forty-eight male Sprague-Dawley rats were randomly assigned to a control group (n = 8) and five model groups (each n = 8), and acute liver injury was assessed at different time points (6, 12, 24, 48 and 72 h) after D-GalN injection. The C-13-MBT, biochemical tests, 15-min retention rate of indocyanine green (ICG(R15)), and liver biopsy were performed and compared between the control and model groups. Correlations between parameters of the C-13-MBT (T-max, MVmax, CUM120 and DOBmax), biochemical tests, ICGR15 and liver necrosis score were also analyzed using Spearman's correlation analysis. RESULTS: T-max, MVmax, CUM120 and DOBmax, as well as most of the traditional methods, correlated with the liver necrosis score (r = 0.493, P < 0.05; r = -0.731, P < 0.01; r = -0.618, P < 0.01; r = -0.592, P < 0.01, respectively). MVmax, CUM120 and DOBmax rapidly decreased and were lower than those in the controls as early as 6 h after D-GalN injection (3.84 +/- 0.84 vs 5.06 +/- 0.78, P < 0.01; 3.35 +/- 0.72 vs 4.21 +/- 1.44, P < 0.05; 52.3 +/- 20.58 vs 75.1 +/- 9.57, P < 0.05, respectively) and reached the lowest point 24 h after D-GalN injection. MVmax, CUM120 and DOBmax returned to normal levels 72 h after D-GalN injection and preceded most of the traditional methods, including liver biopsy. CONCLUSION: The C-13-MBT is a sensitive tool for the timely detection of acute liver injury and early prediction of recovery in a rat model. Further clinical studies are warranted to validate its role in patients with acute liver injury. (C) 2014 Baishideng Publishing Group Inc. All rights reserved.