Serum ferritin reference ranges

Biological role and place in iron metabolism

Total body iron content in humans is about 4.2 grams. Most of this volume is localized in hemoglobin, a key protein that gives blood its red color and ensures oxygen transport to tissues. Specialized protein systems exist to maintain the balance of this vital micronutrient.

While free iron is transported by transferrin, ferritin is responsible for intracellular storage and accumulation. Assessing its serum level forms the basis of laboratory diagnostics, as biochemical markers of iron metabolism change first, reflecting tissue depletion even before visible clinical symptoms develop.

Diagnostic norms and criteria

In medical practice, there is no single universal ferritin norm suitable for absolutely everyone. Reference values can vary significantly depending on the test systems and laboratory used. In addition, normal values in children have pronounced differences from those accepted in the adult population.

To confirm absolute iron deficiency, standardized criteria are used:

• When using the radioimmunoassay method, a level below 10 µg/L is considered the threshold value.
• According to official WHO and UNICEF diagnostic criteria, depletion of stores is established when the indicator drops below 12 µg/L.

According to WHO/UNICEF recommendations, the diagnosis of iron deficiency anemia (IDA) is based on a triad of key laboratory signs: a drop in hemoglobin below the age-adjusted norm, depleted stores (ferritin <12 µg/L), and signs of tissue starvation (soluble transferrin receptor >7 mg/L).

Differential diagnosis of deficiency stages

Analysis of the storage protein level allows the pathological process to be clearly divided into two stages:

1. Latent iron deficiency (LID). At this stage, hemoglobin levels remain completely normal, but serum iron and ferritin are already decreased. The body is consuming tissue reserves.
2. Manifest IDA. Characterized by depletion of reserves (ferritin remains low) against the background of a falling hemoglobin level. Classic hypochromic microcytic anemia develops with a decrease in color index and erythrocyte indices (MCV, MCH, MCHC).

Prescribing iron supplements for hypochromic anemia without reliable evidence of absolute deficiency (primarily without evaluating ferritin) is strictly not recommended. For example, in paroxysmal nocturnal hemoglobinuria, such therapy can provoke severe complications: thrombosis, infections, and renal failure.

Interpretation challenges and modern alternatives

The main drawback of ferritin as a diagnostic marker is that it belongs to acute-phase proteins. Its concentration can falsely rise during inflammatory processes, uremia, or normal pregnancy, masking real iron deficiency.

In such complex clinical situations, modern hematological analyzers come to the rescue, evaluating indicators of iron-deficient erythropoiesis that do not depend on inflammation:

• Ret-He (reticulocyte hemoglobin content) — a decrease below 30.6 pg indicates deficiency.
• HYPO-He (percentage of hypochromic erythrocytes) — an increase in the indicator above 5% indicates depletion.

In addition, during therapy with erythropoiesis-stimulating agents, so-called functional iron deficiency may develop, which requires separate monitoring with simultaneous evaluation of ferritin and transferrin saturation percentage.

Class and exam questions

What else to study on this topic

• Clinical presentation and hematological dynamics in posthemorrhagic IDA
• Transferrin and assessment of total iron-binding capacity (TIBC)
• The role of the soluble transferrin receptor in assessing tissue starvation
• Modern erythropoiesis indicators: Ret-He and HYPO-He
• Functional iron deficiency during therapy with erythropoiesis-stimulating agents

Other topics in the "Additional Topics" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.