The purpose of the study reported in this Research Communication was to evaluate alterations in concentration of total antioxidant capacity (TAC) of plasma, plasma total thiols as markers of oxidative protein damage and malondialdehyde (as a final product of lipid peroxidation) in samples obtained at different stages of the lactation cycle and dry period of dairy cows. We found that TAC was significantly lower in the primiparous cows compared to multiparous cows. This study clearly demonstrates a need for monitoring primiparous cows during the production cycle, especially when they are faced with severe metabolic conditions. Furthermore, TAC may be a sensitive, reliable and useful indicator for measurement of cumulative effects of antioxidants as an addition to metabolic profile tests, which are currently used to analyse dairy cattle health.