ABSTRACT The objective of this study was to evaluate changes in the biochemical parameters of feedlot lambs fed with high concentrations of crude glycerin (GC). Forty crossbred lambs (Dorper × Santa Inês), non-castrated, weighing 21.7±2.7kg and 90 days old, were randomly assigned to four treatments (0, 10, 20, and 30% GC in the diet). To evaluate the biochemical parameters, blood samples (pre-prandial and 4 h after morning feeding) were collected on the first day and the day before slaughter, in each treatment. The high-density lipoprotein was linearly decreased (P<0.0001) when GC concentrations were increased in the diet. Alkaline phosphatase was quadratically affected by treatments (P=0.05), with greater values observed in blood from animals fed intermediate concentrations of CG, and gamma-glutamyl transferase was linearly increased (P=0.008). The blood urea was quadratically affected by treatments with lower values observed in blood from animals fed intermediate concentrations of CG. In conclusion, the replacement of up to 30% (based on dry matter) of corn grain by crude glycerin, in diets for feedlot finishing lambs, does not compromise the health status of these animals.