Objective: to determine the concentrations of clenbuterol in cattle (Bos taurusBos indicus) for human consumption and to detect the alterations that occur in the physiological components.Design/methodology/approximation: This study was developed at the level of municipal trails and livestock farms in several states of the country, with a population of studied animals of 4650 (Bos taurusBos indicus). The study differentiates one control, plus three treatments: a) one is animals with clenbuterol, b) animals with Fasciola hepatica and c) animals with clenbuterol and Fasciola hepatica.Results: The results showed that the values of clenbuterol ranged between 245.123.2 and 1263.462.6 ng / ml, showing that 63.2% of the population of cattle studied had high concentrations of Clb.Limitations on the study/implications: The diagnosis of Clb was made by competitive enzyme immunoassay technique performed on blood serum, however, tissue study was not considered to determine the accumulated Clb concentrations in the liver in the different treatments.Findings/Conclusions: This study demonstrates that clenbuterol masks fascioliasis, since the animals with Fasciola hepaticaclenbuterol showed no symptoms or external changes, but internally mainly in the liver and pancreas (metabolic abnormalities and morphological latter is not shown in this work). It is concluded that clenbuterol produces metabolic abnormalities in Bos taurusBos indicus cattle.