What Is Ferritin in a Blood Test?

Ferritin is the protein that stores iron inside your cells. It is the best single marker of your body's total iron stores.

Normal Ranges

• Men: 20–500 ng/mL
• Women: 20–200 ng/mL
• Optimal functional range: 50–150 ng/mL
• Below 20 = iron deficiency (even before anemia)
• Below 12 = depleted iron stores

Low Ferritin Causes

• Inadequate dietary iron — vegetarian/vegan diets
• Chronic blood loss — heavy menstruation, GI bleeding
• Malabsorption — celiac disease, gastric bypass
• Increased demand — pregnancy, growth
• Endurance exercise

High Ferritin Causes

• Inflammation — ferritin is an acute-phase reactant
• Hemochromatosis — genetic iron overload
• Liver disease
• Alcohol use
• Metabolic syndrome
• Blood transfusions

Important Caveat

• Ferritin rises with inflammation even when iron stores are low
• Check CRP and transferrin saturation if inflammation is suspected