There are several causes of Folate deficiency:

• Inadequate dietary intake, consumption of goats milk, alcoholism. Here, less B12 and folate are absorbed and increased quantities are excreted from the kidneys. 
• Increased demand, in pregnancy, supplementation is required in early pregnancy to reduce the risk of neural tube defects in the developing foetus.  
• Inadequate absorption in patients with bowel disorders. Coeliac disease,  small bowel disease, blind loop syndrome, tropical sprue, post intestinal surgery, cystic fibrosis are the most common.
• Chronic Haemolytic anaemias.

Drugs which affect Folate levels include anticonvulsants, cytotoxic drugs, methotrexate, sulfasalazine, trimethoprim.