The aim of this study was to establish the relationship between parameters of the glucose tolerance test (GTT) of young heifers and their body weight after calving and at the peak of lactation, as well as the level of β-hydroxybutyric acid in blood serum at the peak of lactation. The GTT was conducted on 60 heifers HF at the age of 9-10 months. The animals were infused with 1 g glucose/kg W^0.75 and 10 blood samples were taken at 6 min intervals. For 24 h before taking blood samples the animals received only water. Serum glucose concentrations and insulin activity were estimated. Correlation and regression between the area under the glucose concentration and insulin activity curves, the ratio of these areas (the glin index), maximum insulin activity, peak glucose concentration, glucose half-life, and body weight at the test, after calving and at the peak of lactation, were calculated. The index “glin” seems to be the best parameter for estimation of body weight after calving and at the peak of lactation.