Ferritin
Iron storage protein — reflects total body iron stores and serves as an inflammatory marker.
Optimal Range
40-100 ng/mL (men) · 30-80 ng/mL (women)
Risk-Stratified Targets
| Population / Context | Target |
|---|---|
| Men — optimal | 40–150 ng/mL |
| Premenopausal women — optimal | 30–100 ng/mL |
| Low (investigate even without anemia)Common cause of fatigue, hair loss, restless legs | < 30 ng/mL |
| Elevated (investigate cause)Rule out hemochromatosis, inflammation, liver disease | > 200 ng/mL (women) · > 300 ng/mL (men) |
| Significantly elevatedUrgent evaluation required | > 500 ng/mL |
Why It Matters
Both low and high ferritin are problematic. Low ferritin causes fatigue and impaired oxygen transport. High ferritin (>200) may indicate iron overload, inflammation, or liver disease — all of which accelerate aging through oxidative stress.
Understanding Ferritin
Ferritin is the body's primary iron storage protein, and serum ferritin levels reflect total body iron stores. Iron is essential for oxygen transport (hemoglobin), energy production (mitochondrial cytochromes), DNA synthesis, and immune function. However, iron is unique among minerals in that the body has no active mechanism for excreting excess — making both deficiency and overload clinically significant.
Low ferritin (even with normal hemoglobin) is one of the most common causes of unexplained fatigue, particularly in premenopausal women, endurance athletes, and vegetarians. Symptoms of iron depletion — fatigue, poor exercise tolerance, hair loss, restless legs, difficulty concentrating — can begin at ferritin levels below 30–40 ng/mL, well before frank anemia develops. Many clinicians now treat symptomatic patients with ferritin below 50 ng/mL.
Conversely, elevated ferritin is a red flag that requires investigation. Ferritin rises with iron overload (hereditary hemochromatosis affects 1 in 200 Northern Europeans), but it also rises as an acute-phase reactant in inflammation, liver disease, metabolic syndrome, and infection. Excess iron generates free radicals through the Fenton reaction, causing oxidative damage to organs — particularly the liver, heart, and pancreas. Distinguishing iron overload from inflammatory elevation requires checking transferrin saturation alongside ferritin.