Screening Blood Tests To detect iron deficiency, clinicians should determine hematocrit or hemoglobin as follows: In term infants: At age 9 to 12 months In preterm infants: At age 5 to 6 months In menstruating adolescents: Annually if they have any of the following risk factors: moderate to heavy menses, chronic weight loss, a nutritional deficit, or participation in athletic activity Testing for sickle cell disease can be done at age 6 to 9 months if not done as part of neonatal screening.