In this study pH, temperature of the contents of the forestomach of cows and cow activity were measured using specific smaXtec boluses manufactured for animal care. Rumination time, body weight, milk yield, milk fat/protein ratio, milk lactose, milk somatic cell count, milk electrical conductivity and conception of concentrates were registered with the help of Lely Astronaut® A3 milking robots. The following parameters were obtained: base excess in blood, partial carbon dioxide pressure, partial oxygen pressure, bicarbonate, hydrogen potential, total carbon dioxide carbon, base excess in extracellular fluid, sodium, calcium, potassium, packed cell volume, chlorides, hemoglobin concentration and lactate. According to the concentration of lactose in milk, cows were grouped into two groups: group 1 - milk lactose <4.70% (n = 20), group 2 - milk lactose ≥ 4.70% (n = 15). Data of cows were also divided by milk fat and protein ratio: F/P<1.2 (class 1), F/P=1.2 (class 2) and F/P>1.2 (class 3). According our results we can conclude that inline registered milk lactose concentration can be used as indicator for the health status of fresh dairy cows. Cows with higher lactose concentration (≥ 4.70%) developed more activity (54.47%) and had less risk of mastitis (lover milk EC, and SCC) and metabolic disorders according to F/P. Cows with higher lactose concentration showed higher glucose concentrations. Low level of lactose can be used as indicator of mastitis (milk SCC ≥ 100 thousand/ml) and metabolic disorders according to F/P.