Blood 126 (17): 1981 - 1989, 2015. doi: 10.1182 / blood-2015 - 05 - 642223 Key Points Iron deficiency anemia is usually caused by blood loss (eg, gastrointestinal, menstrual) but may be due to hemolysis, malabsorption, or increased demand for iron (eg, in pregnancy, lactation, periods of rapid growth in children).