What are the normal limits for ferritin (iron storage protein) levels?

Normal Ferritin Limits

Normal serum ferritin values are approximately 135 μg/L for men and 43 μg/L for women in healthy adults, though clinical interpretation requires context-specific thresholds that vary significantly based on patient population and clinical setting. 1

Standard Reference Ranges in Healthy Populations

• Adult men: Mean ferritin is 93-135 μg/L, with an upper limit of normal around 193 ng/mL 1, 2
• Adult women (non-menstruating): Mean ferritin is 34-43 μg/L, with an upper limit of normal around 146 ng/mL 1, 2
• Menstruating women: Ferritin levels typically fall below 30 μg/L when menstruation duration is ≥4 days 3
• Children (6-24 months): Mean ferritin is approximately 30 μg/L 1

The 95% confidence range for normal males extends from 21-447 μg/L, while non-menstruating females range from 26-279 μg/L, reflecting substantial individual variation 3.

Clinical Thresholds for Iron Deficiency

The interpretation of "low" ferritin depends critically on clinical context and presence of inflammation:

In Apparently Healthy Populations

• Ferritin <15 μg/L: Confirms absolute iron deficiency with 99% specificity 1, 4
• Ferritin 15-30 μg/L: Indicates depleted iron stores and generally warrants treatment 1
• Ferritin <35 μg/L: Defines iron deficiency in athletes and general populations 1
• Ferritin <40 μg/L: Observed exclusively in iron deficiency anemia, not other anemia types 3

In Patients with Inflammation or Chronic Disease

Ferritin thresholds must be adjusted upward because ferritin is an acute-phase protein that rises during inflammation, infection, or tissue damage, potentially masking true iron deficiency. 5, 1

• Ferritin <30 ng/mL: Indicates absolute iron deficiency in cancer patients with inflammation 5
• Ferritin <100 ng/mL: Appropriate threshold for iron deficiency in patients with cancer, chronic kidney disease, inflammatory bowel disease, or heart failure 5, 1
• Ferritin <25 ng/mL (males) or <11 ng/mL (females): Defines classic iron deficiency in CKD patients not receiving ESAs 5

In Chronic Kidney Disease (Specific Guidelines)

• Non-hemodialysis CKD: Lower limit for iron therapy is ferritin ≥100 ng/mL 5
• Hemodialysis CKD: Lower limit for iron therapy is ferritin ≥200 ng/mL 5
• Ferritin >500 ng/mL: Not routinely recommended as a target, though IV iron may still be effective in selected patients with transferrin saturation <25% 5

Clinical Thresholds for Iron Overload

• Ferritin >150 μg/L: Rarely occurs with absolute iron deficiency, even in the presence of inflammation 1
• Ferritin 500-1200 ng/mL: In hemodialysis patients with low transferrin saturation (<25%), IV iron may still improve hemoglobin despite elevated ferritin 5

For iron overload screening, ferritin has an estimated sensitivity of 80% and specificity of 65% at various thresholds, with a diagnostic odds ratio of 8, indicating moderate diagnostic utility. 4

Critical Interpretation Caveats

The Inflammation Problem

Ferritin concentration increases independently of iron status during infections, inflammatory conditions, or tissue damage, which can completely mask depleted iron stores. 1, 2

• A sudden increase in ferritin with a drop in transferrin saturation suggests inflammatory iron block rather than true iron sufficiency 1
• In patients with elevated CRP/ESR and ferritin 30-100 μg/L, a mixed picture of true iron deficiency and anemia of chronic disease is present 1
• When ferritin >100 μg/L with elevated inflammatory markers, anemia of chronic disease (inflammatory iron block) is more likely than iron deficiency 1

Complementary Testing Required

Neither ferritin alone nor serum iron alone provides a complete picture—they must be interpreted together with transferrin saturation (TSAT). 1

• TSAT <16%: Sensitive marker for iron deficiency, though specificity is only 40-50% 1
• TSAT <20%: Traditional threshold indicating iron deficiency, particularly relevant in CKD 5, 1
• Calculate TSAT using: (serum iron × 100) ÷ total iron binding capacity 1

The Ferritin-to-Iron Storage Relationship

There is a direct quantitative relationship: 1 μg/L of serum ferritin equals approximately 10 mg of stored iron in the body. 1

This relationship makes ferritin the most specific indicator available for depleted iron stores and the earliest marker of iron deficiency before other parameters become abnormal 1.

Population-Specific Considerations

High-Risk Groups Requiring Lower Thresholds

• Menstruating females: Screen twice yearly; ferritin <35 μg/L warrants intervention 1
• Pregnant women: Use lower thresholds; one study showed 88% sensitivity and 100% specificity for iron deficiency 4
• Athletes: Use <35 μg/L threshold; depleted stores cause fatigue and reduced exercise tolerance even without anemia 1
• Vegetarians/vegans and regular blood donors: Annual screening recommended 1

Special Clinical Scenarios

In patients with hepatitis, cirrhosis, or malignancy, ferritin can be markedly elevated (mean 364 ng/mL in hepatitis/cirrhosis) independent of iron status 2. In breast cancer patients, 41% had elevated ferritin preoperatively (mean 199 ng/mL), rising to 67% with metastatic disease (mean 671 ng/mL) 2.