This article presents a case of insufficiency fracture of medial proximal tibia caused by long-term administration of saccharated ferric oxide (SFO) in a 77-year-old female. In this case, 2-year administration of SFO for iron deficit anemia induced hypophosphatemic osteomalacia and finally resulted in an insufficiency fracture of medial proximal tibia. Hypophosphatemia and pain due to the insufficiency fracture were recovered promptly by withdrawing SFO administration and rest. This case represented varus deformity of the knee associated with osteoarthritis, which may also cause the insufficiency fracture of medial proximal tibia in addition to osteomalacia due to long-term administration of SFO. Long-term SFO administration should be avoided because of a definitive risk of osteomalacia and fragile fracture.