About Iron
Serum iron measures the amount of iron currently circulating in your bloodstream bound to its transport protein, transferrin. It fluctuates significantly throughout the day and is too variable to be meaningful in isolation — it's only useful when interpreted alongside ferritin (your iron stores) and transferrin saturation. Low serum iron with low ferritin confirms iron deficiency; low serum iron with high ferritin usually points to inflammation blocking iron release rather than a true deficiency.