Megaloblastic anemia is an anemia (of macrocytic classification) which results from inhibition of DNA synthesis in re blood cell production. It is often due to deficiency of vitamin B12 and/or folic acid. It can be the result of a lack of intrinsic factor (which lack interferes with B12 absorption), causing pernicious anemia, or with other antimetabolites which poison DNA production, such as chemotherapeutic agents.