Question 1

What ferritin level rules out iron deficiency?

Accepted Answer

In the absence of inflammation, a ferritin >100 ng/mL effectively rules out iron deficiency. With active inflammation (CKD, infection, cancer, autoimmune disease), ferritin can be falsely elevated and a level <300 (some references <500 in CKD) does not rule out deficiency. The transferrin saturation and clinical context become critical.

Question 2

How do I distinguish IDA from anemia of chronic disease?

Accepted Answer

The classic distinction: IDA has low ferritin, high TIBC, and low transferrin saturation. ACD has high ferritin, low or normal TIBC, and low or normal transferrin saturation. The hard case is mixed IDA + ACD — borderline ferritin (30–100) with low Tsat — where soluble transferrin receptor (sTfR) testing can disambiguate.

Question 3

Does a high ferritin always mean iron overload?

Accepted Answer

No. Ferritin is an acute-phase reactant and rises in inflammation, infection, malignancy, hepatocellular injury, and metabolic syndrome. Iron overload requires both elevated ferritin and elevated transferrin saturation (>45%). Ferritin alone, particularly in the presence of inflammation, is much more commonly elevated for non-iron reasons.

Question 4

When should I order HFE genetic testing?

Accepted Answer

Test for HFE C282Y and H63D mutations when transferrin saturation exceeds 45% and ferritin is elevated, particularly in patients of Northern European descent. About 10% of the Northern European population carries one HFE mutation; homozygotes for C282Y are at highest risk for clinical hemochromatosis.

Question 5

What's the next step in microcytic anemia with normal iron studies?

Accepted Answer

Hemoglobin electrophoresis. Beta-thalassemia trait shows elevated HbA2 and HbF; alpha-thalassemia is the diagnosis of exclusion (electrophoresis is normal — molecular testing confirms). Less commonly, sideroblastic anemia or lead poisoning. An elevated MCV / RBC ratio (Mentzer index >13) suggests IDA over thalassemia.

Question 6

How long after starting oral iron should I recheck ferritin?

Accepted Answer

Reticulocyte response is detectable within a week; hemoglobin starts rising at 2 weeks; ferritin recovery lags substantially. A reasonable practice is to recheck ferritin and CBC at 8–12 weeks after starting oral iron, with the goal of normalizing hemoglobin first and then continuing iron for several months to replenish stores.

Pattern	Iron	TIBC	Ferritin	Tsat
IDA	↓	↑	↓	↓
ACD / inflammation	↓	↓ / N	↑	N / ↓
Iron overload	↑	↓	↑↑	↑↑
Thalassemia trait	N	N	N	N

Iron Studies Pattern Interpreter

References

Related