Free erythrocyte protoporphyrin levels in the first year of life.

Free erythrocyte protoporphyrin (FEP) levels were measured in 161 infants judged not to be iron-deficient. In addition to high mean FEP levels in cord blood, a significant number of infants had FEP levels in excess of 120 micrograms/dl red blood cells during the first 6 months of life. These levels are comparable to those found in iron-deficient adults. It is concluded that the clinical significance of an FEP level in excess of 120 micrograms/dl and its value as a marker of early iron deficiency during the first 6 months of life require further study. FEP values in excess of 120 micrograms/dl were not observed in infants aged 7-12 months.