Nieścioruk MW, Kozdroń DJ, Szczepańska P, et al. NORMAL SERUM VITAMIN B12 LEVELS IN SYMPTOMATIC PATIENTS: DIAGNOSTIC VALUE OF METHYLMALONIC ACID AND HOMOCYSTEINE IN FUNCTIONAL DEFICIENCY. IJITSS. 2026;3(2(50). doi:10.31435/ijitss.2(50).2026.5587