Preserving animal populations and improving the quality of life of individual animals largely depends on monitoring their health. This task is especially important in isolated area under the harmful influence of man. The goal of the work was to analyze the mineral composition of the sika deer blood to identify the features of mineral metabolism in isolated area, under conditions of high anthropogenic load. During this research the type of soil on which the habitat of animals is located was taken into account. The object of the study was 59 individuals of sika deer (Cervus nippon) of different sex and age groups living in the territory of the Losiny Ostrov National Park in natural and semifree conditions. The level of serum calcium, phosphorus (and their ratio), magnesium, potassium, iron and chlorides was determined in animal subjects. Biochemical studies of blood samples were carried out on a biochemical analyzer HTI Biohaem SA, using reagents manufactured by ZAO Diacon-DS (Russia). The research results showed that almost all macro and microelements in male sika deer of the younger age group have higher average values relative to those in adult animals. Analysis of mineral metabolism indices in female sika deer revealed that with the same average calcium value in young and adult individuals, the spread between the maximum and minimum levels for this element is more pronounced in the group of adult females (1.7–3.4 mmol/l). Abnormalities of Ca/P metabolism were found in a small number of young males; single deviations in calcium and phosphorus were also observed in males of the older age group. A considerably low magnesium level was found in 31% of the older female deer, while the iron level was 21% higher among the young females. In general, the content of mineral elements in the blood serum of young animals was found to be higher due to the accelerated metabolism and intensive growth. In the course of the work, the indicators of mineral metabolism in sika deer of the Losiny Ostrov National Park were determined, which makes it possible to use this information to observe changes or diagnose metabolic disorders.