GSTM1 and anemia: However, because most other animal models of human iron absorption have been murine models, especially rats, this study was designed to enable further comparisons to previous research using the hemoglobin repletion assay; it is important to note that this assay typically uses a threshold for selecting rats for repletion treatment set at a lower level of anemia, considering that in humans a value of 6 g/dl Hb is the threshold for blood transfusion and anemia is usually assumed at values <10 g/dL.