Serum Iron

Serum Iron measures the amount of iron circulating in the blood, mostly bound to the transport protein transferrin. Levels fluctuate significantly throughout the day (diurnal variation, highest in AM) and are influenced by recent dietary intake. While low levels can contribute to diagnosing iron deficiency, serum iron alone is not a reliable indicator of total body iron stores (ferritin is better) or functional iron status (TSAT is better). It is usually interpreted alongside TIBC and transferrin saturation.