The objective of the study was to determine the effects of the supplemental feeding of glucogenic additive and increasing ruminal degradation of dietary starch on the blood biochemical parameters of high-yielding dairy cows during transition period. The study was carried out on 6 groups (10 animals each) of Polish Holstein-Friesian cows. Measurements of blood indices were carried out as a 2 ×3 experimental design of treatments with factors: glucogenic additive (GA; C – without vs.GA – with) and diet starch ruminal degradation rate (DR; M – maize vs.BW – barley and wheat vs.MBW – maize, barley and wheat). Blood samples were collected 2 weeks prior to calving and 1, 3 and 6 weeks lactation. Notable imp act of the GA in the first weeks post-calving on β-hydroxybutyric acid (BHBA) and nonesterified fatty acids (NEFA) in the blood plasma was noted only in the treatments when the GA supplemented the barley-wheat or maize-barley-wheat ased concentrates, whereas no effect was found when the GA enriched maize-based diets. Irre-spective of grain species, the GA inclusion in the diet has clearly reduced the blood urea and total cholesterol levels, as well as elevated alkaline phosphatase activity