Ferritin
Ferritin
Clinical Overview
Ferritin is the main iron storage protein, found primarily inside cells of the liver, spleen, and bone marrow. A small amount circulates in blood and is the most sensitive serum marker of total body iron stores. Ferritin is also an acute-phase reactant — it rises in inflammation, masking iron deficiency when both conditions coexist.
Why This Test Matters
Ferritin is the best initial test for iron deficiency — it falls before hemoglobin, serum iron, or other markers change. A low ferritin is virtually diagnostic of iron deficiency. However, because ferritin is an acute-phase reactant, a normal or even elevated ferritin does not rule out iron deficiency in patients with chronic inflammation, liver disease, or malignancy — in these cases, transferrin saturation and serum iron should also be measured.
Reference RangesWHO/IFCC standards
| Age Group | Sex | Reference Range | Unit | Notes |
|---|---|---|---|---|
| Adults (18–64) | Male | 20 – 250 | ng/mL | — |
| Adults (18–64) | Female | 10 – 120 | ng/mL | — |
| Elderly (65+) | All | 20 – 300 | ng/mL | — |
Also reported in: µg/L.
Critical (Panic) Values
Critical Low: < 5 ng/mL. Values outside these limits require immediate clinical attention.
What Causes Abnormal Results?
High Ferritin Causes
- Hemochromatosis (hereditary iron overload)
- Chronic liver disease (ferritin stored and released from liver)
- Acute phase reaction (infection, inflammation, malignancy)
- Hemolytic anemia and blood transfusions
- Alcoholism
- Still's disease / adult-onset Still's disease (extremely high ferritin >10,000)
- Macrophage activation syndrome / hemophagocytic lymphohistiocytosis (HLH)
Low Ferritin Causes
- Iron deficiency (most common cause of low ferritin worldwide)
- Pregnancy (increased iron demand)
- Heavy menstrual bleeding (most common cause in reproductive-age women)
- Chronic blood loss (GI bleeding, colorectal cancer)
- Inadequate dietary iron intake (vegetarians, vegans)
Signs & Symptoms to Watch For
How to Prepare for This Test
No fasting required. However, recent acute illness or inflammation will elevate ferritin and mask iron deficiency — consider retesting when the acute illness has resolved.
Factors That Can Affect Results
- Inflammation and infection (acute phase reaction — elevates ferritin, masking deficiency)
- Liver disease (elevated ferritin even without iron overload)
- Alcohol ingestion (raises ferritin)
- Hemolysis (releases ferritin from red cells)
- Recent iron infusion or high-dose oral iron (raises ferritin)
Related Topics
Frequently Asked Questions
What ferritin level indicates iron deficiency?
A ferritin below 12–15 ng/mL is virtually diagnostic of iron deficiency (near 100% specific). Many iron deficiency guidelines recommend treating with iron supplements when ferritin is below 30 ng/mL in symptomatic patients (especially with fatigue, hair loss, or restless legs), even if hemoglobin is still normal. In patients with chronic inflammation, a ferritin up to 100 ng/mL can still mask iron deficiency — transferrin saturation below 20% helps confirm iron-deficient erythropoiesis in this context.
Can ferritin be very high (like 50,000) without iron overload?
Yes. Extremely high ferritin (hyperferritinemia >1,000–10,000 ng/mL) is most often NOT due to iron overload. The most important causes of extreme hyperferritinemia are: adult-onset Still's disease (ferritin is a diagnostic criterion), hemophagocytic lymphohistiocytosis (HLH) — a life-threatening condition where ferritin often exceeds 10,000 ng/mL, liver failure, and severe infections (sepsis, COVID-19). These conditions require urgent evaluation. Hereditary hemochromatosis typically causes ferritin in the hundreds to low thousands range.