Iron deficiency in the postpartum period is common and associated with impaired quality of life. Interpretation of ordinary laboratory parameters is considered to be simple in postpartum women, as normalization of pregnancy induced physiological changes is assumed to take place in the early postpartum period. We have studied changes in erythrocyte and iron parameters during the first 11 postpartum months. Erythrocyte parameters and iron markers, serum ferritin, and soluble transferrin receptor (sTfR), and an inflammation marker, neopterin, were investigated in healthy mothers 6 weeks (n = 104), 4 months (n = 100), and 11 months (n = 43) after giving birth to a term infant. Healthy nonpregnant and nonlactating women (n = 61) were included as controls. The hemoglobin level increased throughout the first 11 postpartum months and was significantly higher from 4 months on, compared to control women. At all time points, the mothers had significantly lower mean corpuscular volume (MCV) and higher erythrocyte count and percentage of hypochromic erythrocytes. sTfR levels were significantly higher over the whole serum ferritin distribution during the first 4 postpartum months compared to the controls, indicative of an increased cell production. At 6 weeks, postpartum mothers had higher neopterin levels and this was associated with markers of a low iron status, not including sTfR. Substantial changes in erythrocyte and iron parameters were observed in the postpartum period, consistent with an increased, but iron restricted erythropoiesis. The increased erythropoietic activity was reflected in higher sTfR concentrations. Given the vital role for iron in both mothers and infants, further studies are warranted for establishing proper cut off levels for sTfR as an iron marker in postpartum women.