One of the oldest problems in which modern scientific medicine has interested itself is that concerning the efficacy of iron in the treatment of anemia. Perhaps no other problem has attracted so much thought and work with results so little in agreement. This idea has been expressed well by Whipple and Robscheit-Robbins:1 "The history of anemia treatment with drugs is indeed a tale to make the judicious grieve."
Some of the conflicting ideas regarding iron medication may be traced to the careless application of the discoveries made in experimental anemia in animals to the anemias that occur in man. For the present, until more is known of the mechanisms involved in different types of anemia, in man and animals, the statement of Witts is much to the point, namely, that no apology is needed for considering the field of clinical medicine the testing ground of iron therapy.2
HEATH CW. ORAL ADMINISTRATION OF IRON IN HYPOCHROMIC ANEMIA. Arch Intern Med (Chic). 1933;51(3):459-482. doi:10.1001/archinte.1933.00150220134011