Converted to tetrahydrofolic acid (THF), a coenzyme for 1-carbon transfer/methylation reactions.- Important for the synthesis of nitrogenous bases in DNA and RNA.

- Found in leafy green vegetables. - Absorbed in jejunum. Small reserve pool stored primarily in the liver.

Deficiency:- Macrocytic, megaloblastic anemia; hypersegmented polymorphonuclear cells (PMNs)- Glossitis- No neurologic symptoms (as opposed to vitamin B₁₂ deficiency)- Labs: ↑ homocysteine, normal methylmalonic acid levels- Seen in alcoholism and pregnancy

- Deficiency can be caused by drugs (eg, phenytoin, sulfonamides, methotrexate).

- Supplemental maternal folic acid at least 1 month prior to conception and during early pregnancy ↓ risk of neural tube defects.