Clinical Information

Iron (Fe) is involved in the function of all cells. Systemic iron homeostasis is maintained by the tight regulation of communication between cells that absorb iron from the diet (duodenal enterocytes), cells that consume iron (mainly erythroid precursors), and cells that store iron (hepatocyte and tissue macrophages). Once ingested iron is absorbed and temporarily stored in the mucosal cells within ferritin. Ferritin provides a soluble protein shell to encapsulate a complex of insoluble ferric hydroxide and ferric phosphate. Iron is released into the blood and transported as Fe (III)-transferrin.(1)

The concentration of iron varies widely, both in normal healthy persons, and in various clinical disorders. The biologic variation of iron is notable in normal healthy persons and in various clinical disorders owing to both diurnal variation and post-prandial effects. Normally, intra-individual serum iron levels undergo significant within day and day-to-day variation. The intraindividual day-to-day variation of iron is approximately 25% to 30%.(1) Serum iron concentration is frequently highest in the morning and declines progressively during the day, to reach a low point near midnight. There are no definitive studies that suggest fasting from food is required; however, serum iron is commonly drawn in the fasting state. Drawing blood three hours after consuming oral iron supplements has been shown to significantly increase serum iron concentration 3 to 5-fold and therefore should be avoided for 24 hours prior to collection.(2)