Folic acid is most commonly recommended in the preconception period and early pregnancy because neural tube development occurs very early. Supplementation may also be considered when folate deficiency is documented, diets are limited, alcohol use is chronic, malabsorption is suspected, or certain medications are involved—always based on clinical judgment. The best practice is not “everyone should take it,” but rather risk stratification (labs + clinical context) and targeted dosing. If folic acid is used longer-term, vitamin B12 status should not be ignored, given their shared pathways and the masking risk.