The American Society of Hematology (ASH) has published its first guideline on diagnosing iron deficiency, setting higher serum ferritin thresholds across several patient populations, whether or not anemia is present. The panel included pediatric and adult hematologists, a neonatologist, a maternal-fetal medicine specialist, a pharmacist, and a patient representative. Its goal was for generalists and specialists alike to apply the same thresholds.