Iron, TIBC and Ferritin Panel

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.

Total Iron Binding Capacity (TIBC) measures the blood's capacity to bind iron with transferrin, indirectly reflecting the amount of available transferrin. In iron deficiency, the body produces more transferrin to capture scarce iron, leading to a high TIBC. Conversely, in iron overload or chronic inflammation/infection (transferrin is a negative acute phase reactant), TIBC is often low or normal.

Transferrin Saturation (TSAT), often called Iron Saturation, calculates the percentage of iron-binding sites on transferrin that are occupied by iron (TSAT % = [Serum Iron / TIBC] x 100, or calculated using transferrin). It reflects how much iron is readily available for delivery to tissues.

• Low TSAT (<15-20%) is a key indicator of functional iron deficiency (insufficient iron delivery for erythropoiesis), even if ferritin is normal/high due to inflammation.
• High TSAT (>45-50%, especially >55-60%) suggests increased iron load and potential risk for iron overload (e.g., hemochromatosis).

Ferritin is the most sensitive test for iron stores in the body, but it can also be elevated during inflammation, which can mask iron deficiency. Use our Iron Status Interpreter for a comprehensive assessment of your iron levels.