2017 Volume 60 Issue 2 Pages 98-102
A 78-year-old man developed megaloblastic anemia (hemoglobin 11.5 g/dL, mean corpuscular volume [MCV] 109 fL) 3.8 years after metformin was first administered. Because we suspected that metformin had induced megaloblastic anemia, metformin administration was immediately discontinued. Thereafter, the hemoglobin and MCV levels improved (13.6 g/dL and 104 fL, respectively) immediately after administration of oral and intramuscular cobalamin for approximately 1 month. Biguanide has recently been used to treat type 2 diabetes. Therefore, we must be careful when administering particularly high doses of metformin because of the gradual and delayed progression of megaloblastic anemia after metformin administration.
