This article reports simple, green and efficient synthesis of gamma-Fe2O3 nanoparticles (NPs) (maghemite) through single-source precursor approach for colorimetric estimation of human glucose level. The gamma-Fe2O3 NPs, having cubic morphology with an average particle size of 30 nm, exhibited effective peroxidase-like activity through the catalytic oxidation of peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2 producing a blue-colored solution. On the basis of this colored-reaction, we have developed a simple, cheap, highly sensitive and selective colorimetric method for estimation of glucose using gamma-Fe2O3/TMB/glucose-glucose oxidase (GOx) system in the linear range from 1 to 80 mu M with detection limit of 0.21 mu M. The proposed glucose sensor displays faster response, good stability, reproducibility and anti-interference ability. Based on this simple reaction process, human blood and urine glucose level can be monitored conveniently. (C) 2014 Elsevier Inc. All rights reserved.