Microglia cells are the resident innate immune cells in the central nervous system (CNS). The function of microglia cells is tightly linked with their morphological presentation, which is in itself influenced by the conditions, factors and mediators to which microglia cells are exposed. It is in this manner we identify two basic fenotypes, M1 and M2, as well as a transitional, M1/M2 mixed form. The M1 fenotype is usually metabolically linked to the process of aerobic glycoliss and the increased production of lactates, while the M2 ramified fenotype is usually metabolically linked to the process of oxidative phosphorylation and the calming of inflammation. The goal of this research was to discover whether fetuin, an active ingredient in FCS, influenced the polarization state (M1/M2) with fenotype and metabolic changes of BV-2 cells that followed in-vitro. Cultures grown without FCS, through a period of 96 hours, demonstrated morphological and functional characteristic of resting M2, ramified microglia cells, including an increase in expression of M2-specific immunoflorescence markers (CD206). By identifying the factor that shift the M1/M2 balance in the central nervous system towards the M2 fenotype, doors are opened into new therapeutic options for conditions that have metabolic stress at its base (oxygen radicals, iNOS, lactate), caused by chronic neuroinflammation (neurodegenerative diseases, psychiatric disorders, chronic pain syndromes and diabetes type II).