Ferritin Blood Test

What Does This Test Measure?

Ferritin is the primary iron storage protein. Serum ferritin reflects total body iron stores and is the single best test for diagnosing iron deficiency. Ferritin is also an acute phase reactant; it rises with inflammation, infection, liver disease, and malignancy, independent of iron status.

Why Your Doctor Ordered This Test

Doctors order ferritin as the primary screening test for iron deficiency before anemia develops, because ferritin drops early as iron stores deplete, even when hemoglobin remains normal. It is essential in evaluating unexplained fatigue, restless legs syndrome, poor concentration, pica (craving ice or dirt), and brittle nails, all potential symptoms of iron deficiency without overt anemia. In premenopausal women with heavy menstrual bleeding, ferritin detects subclinical iron depletion that may contribute to chronic fatigue. In pregnant women, ferritin helps guide supplementation to prevent maternal and fetal complications. In infants and children, ferritin screens for iron deficiency that can impair neurodevelopment.

Doctors also order ferritin to evaluate possible iron overload conditions, hereditary hemochromatosis (especially HFE C282Y/H63D mutations) presents with elevated ferritin and transferrin saturation. When ferritin exceeds 300 ng/mL in men or 200 ng/mL in women, physicians check for iron overload with genetic testing and liver iron quantification. In inflammatory or chronic disease states, ferritin is measured as an acute phase reactant to assess the intensity of inflammation; markedly elevated values (>1,000 ng/mL) prompt investigation for adult-onset Still’s disease, hemophagocytic lymphohistiocytosis (HLH), or severe COVID-19 cytokine storm. Oncologists monitor ferritin in certain leukemias and lymphomas. Nephrologists track ferritin in chronic kidney disease to manage anemia of renal failure and guide intravenous iron and erythropoietin therapy. Thus, ferritin serves both iron status and inflammatory assessments.

What High Ferritin Means

High ferritin can reflect: iron overload (hereditary hemochromatosis, HFE gene mutations, ferritin often >300 in men, >200 in women, with elevated transferrin saturation), multiple blood transfusions (transfusional iron overload), inflammation/infection (acute phase reactant, ferritin rises dramatically), liver disease (hepatitis, fatty liver, alcohol), metabolic syndrome (strongly associated with elevated ferritin), malignancy, and the very rare hemophagocytic lymphohistiocytosis (HLH, extreme hyperferritinemia, often >10,000). An elevated ferritin >1,000 warrants investigation for iron overload.

What Low Ferritin Means

Low ferritin is the gold standard for iron deficiency diagnosis. Ferritin <30 ng/mL is essentially diagnostic. Ferritin 30–100 ng/mL with low MCV, low MCH, low serum iron, and high TIBC indicates iron deficiency. Ferritin 30–100 ng/mL with normal indices and normal iron studies may represent early iron depletion (low stores, not yet anemic). Causes: chronic blood loss (GI bleed, ulcer, polyp, cancer; heavy menstruation), poor dietary intake (vegetarian/vegan without supplementation), malabsorption (celiac disease, gastric bypass, H. pylori), and increased demand (pregnancy, growth, intense endurance training).

How to Prepare and What Affects the Result

Preparation for a ferritin blood test is straightforward, but attention to timing and interfering factors improves accuracy. Standard serum ferritin does not require fasting; however, if the iron panel (serum iron, TIBC) is ordered simultaneously, an 8- to 12-hour overnight fast is recommended because iron levels fluctuate with meals. The test can be drawn at any time of day, but consistency is key for serial monitoring.

Certain medications and supplements drastically alter results: oral iron supplements (ferrous sulfate, ferrous gluconate) can transiently raise serum iron and ferritin if taken shortly before blood draw, advise stopping iron supplements for 24 hours prior. High-dose biotin (vitamin B7) supplements, often found in hair/skin/nail formulations, can interfere with the immunoassay used for ferritin and produce falsely low values; discontinue biotin at least 72 hours before testing. Liver conditions and alcohol consumption within 24 hours can spike ferritin as an acute-phase reactant. Recent vigorous exercise also elevates ferritin due to muscle inflammation, so the patient should rest for 24 hours. The blood sample is stable as serum (red-top tube) or plasma, but hemolysis should be avoided because it can release intracellular ferritin and falsely increase the result.

Common Misinterpretations

One major misinterpretation is equating high ferritin with iron overload without checking concurrent inflammation. Ferritin is an acute-phase reactant, so an elevated ferritin in the setting of infection, autoimmune flare (rheumatoid arthritis, lupus), or recent surgery often reflects systemic inflammation rather than true iron excess. Clinicians who order only ferritin without transferrin saturation risk misdiagnosing hemochromatosis or missing it; a saturation below 45% with high ferritin suggests inflammation or metabolic syndrome, while a saturation above 45% indicates possible HFE hemochromatosis. Another error is diagnosing iron deficiency based on a “normal” ferritin in the presence of inflammation. In chronic kidney disease, heart failure, or inflammatory bowel disease, ferritin rises as an acute-phase protein, so a ferritin of 80–150 ng/mL can still mask true iron deficiency. In such cases, a low transferrin saturation (<20%) or elevated soluble transferrin receptor would reveal functional iron deficiency despite normal ferritin. This is why ferritin alone can miss iron-restricted erythropoiesis.

A second common misinterpretation is using the same lower cut-off for everyone. A ferritin below 30 ng/mL is almost certainly iron deficiency in all adults, but premenopausal women, children, and athletes often have symptoms of iron deficiency without anemia at ferritin levels of 30–50 ng/mL because tissue iron depletion occurs before hemoglobin drops. Yet many labs still report normal ranges as low as 10–15 ng/mL, which can delay diagnosis. Conversely, interpreting high ferritin purely as hemochromatosis ignores the very common metabolic syndrome: individuals with obesity, fatty liver, and insulin resistance frequently have ferritin levels between 200–500 ng/mL due to hepatic iron deposition and subclinical inflammation. Without checking LFTs, HbA1c, and abdominal imaging, this may be mislabeled as iron overload. Additionally, extreme hyperferritinemia (>10,000 ng/mL) is often mistaken for HLH when infection-associated hemophagocytosis, liver failure, or massive transfusion can raise ferritin comparably; clinical context and percent glycosylated ferritin (low in HLH) help differentiate.

Frequently Asked Questions

What does low ferritin indicate?

Low ferritin is the most reliable indicator of depleted iron stores and iron deficiency. Even before hemoglobin drops, ferritin below 30 ng/mL confirms iron deficiency. Levels between 30–50 ng/mL can cause fatigue, hair loss, and restless legs due to early tissue iron depletion. Common causes include chronic blood loss (heavy periods, GI bleeding), poor dietary intake, malabsorption disorders like celiac disease, or increased demands in pregnancy and growth.

What does high ferritin mean?

High ferritin can result from iron overload conditions like hereditary hemochromatosis, where ferritin often exceeds 300 ng/mL in men and 200 ng/mL in women with elevated transferrin saturation. It also rises sharply with inflammation, infection, liver disease, and metabolic syndrome, even when iron stores are normal. Extreme elevations >1,000 ng/mL prompt investigation for hemophagocytic lymphohistiocytosis (HLH), severe infections, or malignancies, not just iron excess.

Can ferritin be normal even with iron deficiency?

Yes, ferritin can appear normal or even elevated in the presence of iron deficiency when inflammation is present. Because ferritin is an acute phase reactant, conditions like chronic kidney disease, rheumatoid arthritis, or cancer can raise ferritin and mask low iron stores. In these cases, a transferrin saturation below 20% or elevated soluble transferrin receptor suggests true functional iron deficiency despite a ferritin of 80–150 ng/mL.

How can I raise my ferritin levels naturally?

Dietary changes can gradually improve ferritin when deficiency is mild. Increase intake of heme iron from red meat, poultry, and seafood, which is better absorbed. Pair non-heme iron sources (spinach, lentils, tofu) with vitamin C to boost absorption. Avoid coffee, tea, and calcium supplements near iron-rich meals as they inhibit uptake. Cooking in cast iron pans adds some iron, but significant deficiency often requires oral iron supplements prescribed based on severity.

What causes ferritin to be extremely high (>1,000 ng/mL)?

Ferritin above 1,000 ng/mL is strongly associated with hemophagocytic lymphohistiocytosis (HLH), a life‑threatening hyperinflammatory syndrome. But it also occurs in severe infections (COVID‑19, sepsis), acute liver failure, massive transfusions, and certain hematologic malignancies. In adult‑onset Still’s disease, ferritin can soar. Distinguishing requires clinical context, percent glycosylated ferritin (very low in HLH), and other markers like triglycerides and fibrinogen to avoid missing the underlying trigger.

Related Markers: Read Together for Full Context

BloodWorker reads lab values together, not in isolation. These related markers provide essential context for interpreting your Ferritin result: