Since the persistent decrease in blood glucose during late pregnancy in sheep is an index of high risk of metabolic disorder, the present study aimed to evaluate the capacity of the serum fructosamine (Fser) to retrospectively monitor blood glucose. Pregnant grazing sheep were assigned to three treatments: high energy (n = 8), supplemented with 400 g of corn grain from Day 100 until lambing; medium energy (n = 7), not supplemented, and low energy (n = 8), fasted from Days 136 to 141. In weekly blood samples (7 weeks before to 3 weeks after lambing), glucose, fructosamine, β-hydroxybutyrate and total proteins were determined. Serum protein were stable and without differences among groups. β-hydroxybutyrate was higher in the fasted group the week after fasting (P < 0.05). The regression analysis between plasma glucose and Fser in the same week and in the 3 weeks following, showed no significant correlations, actual or retrospective, neither considering all sheep nor within each energy level. The results did not support the usefulness of Fser for monitoring plasma glucose concentration in late pregnant ewes.