After intramuscular injection iron dextran is absorbed primarily through the lymphatic system: most is absorbed after 3 days and the remainder over 3 to 4 weeks. A variable portion may become fixed in the muscle for several weeks or months. Following the i.v.

infusion the iron dextran is rapidly taken up by the cells in the reticuloendothelial system (RES), particularly in the liver and spleen from where iron is slowly released and bound to proteins. . The iron is immediately bound to the available protein moieties to form hemosiderin or ferritin, the physiological forms of iron, or to a lesser extent,  to transferrin.

most absorbed iron is bound to transferrin and transported to bone marrow where it is incorported into heamoglobin , the remainder contained within the storage form , ferritin or haemosiderin , with smaller amounts occurring in plasma bound to transferrin negligible amounts of iron are lost via the urinary or faeces .
Dextran is either metabolised or excreted.