The study was carried out on 48 purebred Arabian mares in the Białka Stud (Lublin region). Blood indicators (haematological, biochemical, immunological) and heart rate changes during blood collection were determined in the last four months of pregnancy and in six lactation months. Milk testing (bacteriological, cytological, chemical) was conducted during the entire lactation. The majority of determined indices showed significant (P<0.05) or highly significant (P<0.01) differences during pregnancy and lactation. The levels of some indices (lymphocytes, segmented neutrophils, neutrophil/lymphocyte (N/L) ratio, AST, LDH, TG, haptoglobin) were similar in the last month of pregnancy and the first lactation month so they can be classified among periparturient symptoms. The milk protein and fat contents and somatic cell count showed a decrease, whereas the lactose level slightly increased over the duration of the suckling period. Knowledge of the mares' metabolic profile and changes in emotional balance in specific physiological periods can be useful in assessing if the pregnancy and lactation are proceeding correctly, which is important for breeding success.