Ferritin and Iron Testing: Detecting and Managing Iron Deficiency
Iron deficiency is the most common nutrient deficiency in adults, especially menstruating women — and it hides in a normal CBC.
Why ferritin is the first test
Ferritin is the body's iron storage protein. A low ferritin means depleted iron stores — and this happens long before hemoglobin drops enough to call it anemia. That is why relying on a CBC alone underdiagnoses iron deficiency.
Practical thresholds (context-dependent): ferritin below 30 µg/L is consistent with iron deficiency in most adults; below 15 µg/L is diagnostic. Symptoms of low iron (fatigue, hair thinning, restless legs, exercise intolerance, cold intolerance) often appear at ferritin values under 50 µg/L.
When to add a full iron panel
Serum iron, transferrin (or TIBC), and transferrin saturation (TSAT) are added when ferritin is borderline, when inflammation is present (ferritin is an acute-phase reactant and can be falsely normal), or when hemochromatosis is suspected (very high ferritin with elevated TSAT).
Treatment and follow-up
Oral iron (ferrous sulfate, gluconate, or bisglycinate) at 60–120 mg elemental iron every second day (better tolerated and absorbed than daily) with vitamin C, away from calcium and coffee, is first-line for most adults. Recheck ferritin after 8–12 weeks.
IV iron is considered when oral iron fails, is not tolerated, or when replenishment must be rapid. Underlying causes — menstrual blood loss, celiac disease, chronic GI blood loss — should always be investigated when iron deficiency recurs.
Add ferritin to your next draw
Ready to book? Reserve a private blood collection appointment on our Book Blood Collection page, or request a private requisition through blood test prescription.
Frequently asked questions
My hemoglobin is normal — can I still be iron deficient?+
Yes. Iron deficiency without anemia is common and symptomatic; ferritin is the test that detects it.
Should I take iron with food?+
Take on an empty stomach with vitamin C when tolerated; with a small snack if it causes nausea.