Iron

Overview

Iron measures the concentration of this essential trace metal in blood, primarily bound to transferrin, and reflects circulating iron available for erythropoiesis. Iron is a key component of hemoglobin, myoglobin, and various metalloenzymes involved in oxygen transport and cellular respiration. Low serum iron can indicate iron deficiency anemia, chronic disease, or blood loss, whereas high levels may signal iron overload (e.g., hereditary hemochromatosis, repeated transfusions, or acute iron poisoning). Iron testing is clinically useful as part of an iron‑panel (with ferritin, transferrin, and TIBC) to evaluate anemia, iron deficiency, and iron‑overload conditions.

Clinical Use Cases

  • Evaluating iron deficiency anemia and distinguishing it from anemia of chronic disease.
  • Monitoring patients with iron‑overload disorders (e.g., hemochromatosis, thalassemia with transfusions).
  • Assessing iron status in pregnancy, chronic kidney disease, or gastrointestinal blood loss.
  • Investigating suspected acute iron overdose.

Specimen Types

  • Serum (most commonly used).
  • Plasma (less common; serum is standard for traditional iron assays).

Measurement Methods

  • Colorimetric assay after reduction of Fe³⁺ to Fe²⁺ and formation of a chromogen (e.g., ferrozine or similar reagent).
  • Automated clinical chemistry analyzers using standardized spectrophotometric methods.
  • Indirectly via calculation of transferrin saturation when serum iron and total iron‑binding capacity (TIBC) are measured.

Test Preparation and Influencing Factors

  • Ideally measured in the morning after an 8–12‑hour fast, because iron exhibits diurnal variation and can rise after meals.
  • Oral iron supplements, recent blood transfusion, or iron‑infusion therapy falsely elevate serum iron.
  • Inflammation and acute‑phase reactions lower serum iron even when tissue iron is adequate.
  • Hemolysis during phlebotomy or sample handling can increase measured iron levels.

Synonyms

  • Serum iron.
  • Fe (chemical symbol).
  • Iron, total serum iron.

Further Reading