IRON

Serum iron measures the amount of iron circulating in your blood bound to its transport protein, transferrin. The value reflects the iron available at this moment for delivery to the bone marrow (for haemoglobin synthesis) and to other tissues. It is highly variable through the day — typically highest in the morning and lowest in the evening — and influenced by recent meals, iron supplements, and inflammation.

Serum iron by itself is rarely interpreted alone. It is part of the "Iron Studies" panel along with Total Iron Binding Capacity (TIBC), transferrin saturation (calculated as iron/TIBC), and ferritin (the iron storage form). The combination distinguishes iron deficiency (low iron, high TIBC, low saturation, low ferritin) from anaemia of chronic disease (low iron, low TIBC, low saturation, normal-to-high ferritin) and from iron overload (high iron, high saturation, high ferritin).

Iron deficiency is the most common cause of anaemia in India — affecting 50–60% of women, 40% of pregnant women, and 60–70% of preschool children (NFHS-5 data). A solo serum iron is not sufficient to diagnose iron deficiency because it fluctuates so much, but in combination with the full iron profile and ferritin it confirms the cause of microcytic anaemia and guides oral or intravenous iron therapy.

For patients with persistent anaemia or unexplained fatigue, iron studies are essential before starting iron supplementation. Empirical iron therapy without confirming iron deficiency can mask underlying disease (thalassemia trait, chronic disease) and rarely cause iron overload.

Fast for 8–10 hours. Avoid iron supplements for 24 hours before the test (they can cause a transient spike in serum iron). Take the sample in the morning if possible — iron levels have a diurnal rhythm and are highest between 8 and 10 AM. Disclose any oral iron tablets, multivitamin use, recent transfusion, or current infection (acute inflammation lowers serum iron).