Abstract: The aim of present study was to evaluate the functional efficiency of probiotic preparation on selected blood biochemical parameters of ISA Brown hens. Feed in the experimental group of hens was enriched with a probiotic preparation in the dose of 500g.t-1 consisted of freeze-dried cultures: Lactobacillus bulgaricus LAT 187, L. acidophilus LAT 180, L. helveticus LAT 179, L. delbrueckii ssp. Lactis LAT 182, Streptococcus thermophiles LAT 205, Enterococcus faecium E-253 with concentration of 5.109 (CFU LAB) living organisms in 1 gram. Blood samples were collected in 25 and 48 week of hens’ age. Biochemical parameters of mineral profile (calcium, phosphorus, magnesium, sodium, potassium, chlorides), energetic profile (plasma total cholesterol, triglycerides, total proteins, bilirubin, glucose), and activities of serum liver enzymes (aspartate aminotransferase AST, alanine aminotransferase ALT, alkaline phosphatase ALP) were analysed using Ecoline kits and a semi-automated clinical chemistry analyser Microlab 300 (Vilat Scientific, Dieren, The Nederland). Probiotic preparation reduced (P<0.05) serum cholesterol and triglycerides content. No significant effects of probiotic on remaining parameters were confirmed.