This paper is a review of established methods of folate status assessment and the primary factors that increase the risk of folate deficiency, including physiological life cycle changes. The first stage of folate depletion can be assessed by measuring serum folate levels, which drop prior to tissue depletion, and which are paralleled by a reduction in red blood cell (RBC) folate. Functional changes associated with abnormalities in biochemical pathways can be monitored by the deoxyuridine suppression test. Cell division, including erythropoiesis, becomes impaired in the same time sequence as changes in biochemical functions, as evidenced by abnormal erythrocyte morphology and a reduction in hemoglobin concentration. In addition to inadequate dietary folate intake, key factors that may impair folate utilization and thus status include alcohol consumption, smoking, and specific drugs. Folate requirements may increase during various phases of the life cycle due to physiological stresses such as pregnancy and lactation. Folate status may also be compromised during adolescence and in senescence for diverse reasons that require special emphasis on factors such as biological maturity and socioeconomic status, as well as chronic use of alcohol, drugs, and smoking.