This study utilizes liquid chromatography/mass spectrometry (LC-MS) to analyze the plasma of four groups of four healthy male and female subjects administered high doses of pure limonin glucoside (0.25-2.0 g in 200 mL of buffered water) for the presence of limonin to establish the absorption, metabolism, and bioavailability of citrus limonoids to humans. The plasma analysis revealed increasing amounts of limonin associated with increasing doses of limonin glucoside among the subject groups in mean maximum concentration amounts ranging from 1.74 to 5.27 nmol/L. A high degree of variability in the analyzed limonin concentration was observed within the subject groups. The mean time to maximum concentration was 6 h. A second compound with MS/MS characteristics identical to limonin was detected in amounts up to 5.13 nmol/L and is hypothesized to be a limonin epimer. Poststudy health evaluation established no ill effects among study subjects consuming high doses of limonin glucoside.