 The study found that when Hb>10, EPO mean was 20.6 and when Hb≤10, EPO mean was 26.8.As Hb goes down, EPO goes up.While the reason for this decreased response is not fully understood, Strauss (n.d.) states that it results from both physiological factors (e.g., the rapid rate of growth and need for a commensurate increase in RBC mass to accompany the increase in blood volume) and, in sick premature infants, from phlebotomy blood losses.