The trial was carried out to evaluate the effects of dietary urea level on serum urea, glucose and amino acids concentrations. Eighteen clinically healthy ewes were previously adapted to urea feeding (initial body weight 33.81 kg and about 4 years age). Animals were randomly assigned to three groups; the control group was given basal diet which met energy and protein requirements for body weight maintenance and the other two groups were fed on basal diet with 1% and 1.5% urea on dry matter (DM) basis to replace part of the dietary crude protein. The duration of this study was lasted for 3.5 months. Animals were kept in individual pens. The estrous cycles were synchronized using two injections of prostaglandin (PGF_2α). Blood samples were taken at the beginning of the experiment as well as at the first and second injection with PGF_2α and then just before slaughter. Three animals were slaughtered at follicular phase and the remaining three animals were at luteal phase in each group. The follicular and luteal phases were monitored 40 hrs and 10 days upon second injection with PGF_2α. Serum glucose and urea concentrations were determined using spectrophotometer. Essential and non essential amino acids were determined using HPLC method in blood plasma collected at follicular and luteal phases. The results indicated that serum urea levels in treated groups were significantly higher than those in the control one (P<0.05), and vice versa with serum glucose concentrations. There were no significant differences in plasma essential and non essential amino acids during follicular and luteal phases among the three groups. It could be concluded that dietary 1% and 1.5% urea level changes serum concentrations of urea and glucose but did not affect plasma amino acids.