Folate deficiency is a low level of folic acid in the body. Also known as vitamin B9, it is involved in adenosine, guanine, and thymidine synthesis (part of DNA synthesis). Signs of folate deficiency are often subtle. Anemia is a late finding in folate deficiency. Folate deficiency anemia is the term given for this medical condition. Characterized by the appearance of large-sized, abnormal red blood cells (megaloblasts), which form when there are inadequate stores of folic acid within the body.