Serum homocysteine levels are assessed by measuring the total concentration of the amino acid homocysteine in the blood. Homocysteine undergoes conversion into cysteine and methionine with the assistance of several B vitamins. This test helps healthcare professionals identify vitamin B6, B12, or folic acid deficiencies and diagnose conditions like homocystinuria and various metabolic, cardiovascular, cerebrovascular, and thromboembolic disorders.