Aim. Increasingly, researchers note oxidative stress among the pathophysiological factors of the metabolic syndrome (MetS) [1]. Oxidative stress causes peroxidation of erythrocyte membrane lipids with subsequent desialyation, which leads to an increase in the concentration of sialic acids in the blood plasma and causes the aggregation of these cells [2]. Many studies indicate that the substances obtained from the medicinal mushroom Ganoderma lucidum (polysaccharides, triterpenoids, polyphenols) have a high antioxidant potential [3], and therefore, the work aimed to investigate the ability of G. lucidum extract to influence the number of erythrocytes and their precursors, as well as the concentration of sialic acids in erythrocytes and blood plasma under experimental MetS. Conclusions. We found a positive corrective effect of G. lucidum extract on the concentration of sialic acids in erythrocytes and blood plasma of rats. The obtained results demonstrate the promising use of this medicinal mushroom for the correction of dysfunction of the blood system under MetS.