Iron status definitions. * More specific tests may be needed (e.g., reticulocyte hemoglobin content, hypochromic red blood cells, serum transferrin receptors) to confirm iron deficiency. ** For surgeries with expected hemoglobin drop >3–4 g/dL due to bleeding; 1 ng/mL ferritin ≈8 mg stored iron [adapted from references 5, 16, 19].