However, folate deficiency can occur in a number of other situations, such as pregnancy or cancer, resulting in increased rates of cell division and metabolism and thereby causing an increase in the body's demand for folate (46).
Several medications may also contribute to deficiency (see Safety).
Rapidly dividing cells are most vulnerable to the effects of vitamin B9 (folate) deficiency; thus, when the folate supply to the rapidly dividing cells of the bone marrow is inadequate, blood cell division becomes abnormal resulting in fewer but larger red blood cells (‘megaloblastic’ or ‘macrocytic anemia’). Progression of such an anemia ─ identical to the megaloblastic anemia resulting from vitamin B12 deficiency ─ leads to a decreased oxygen-carrying capacity of the blood and may ultimately result in symptoms of fatigue, weakness, and shortness of breath (1).
Individuals in the early stages of folate deficiency may not show obvious symptoms, but blood levels of homocysteine may increase.
Authored by Dr Peter Engel in 2010, reviewed and revised by Angelika Friedel on 29.06.2017