Normal Serum Ferritin Levels in a 40-Year-Old Female
The normal serum ferritin range for a 40-year-old premenopausal woman is 20-200 μg/L, with an average value of approximately 35-43 μg/L. 1, 2
Standard Reference Intervals
The European Society for Clinical Nutrition and Metabolism (ESPEN) establishes the normal serum ferritin range for adult women as 20-200 μg/L. 1
The American Association for the Study of Liver Diseases (AASLD) provides a slightly narrower range of 15-150 μg/L for women. 1
Population studies demonstrate that the median serum ferritin in 40-year-old women is approximately 38 μg/L, with a 5-95 percentile range of 6-135 μg/L. 3
The Centers for Disease Control and Prevention (CDC) reports an average serum ferritin value of 43 μg/L for adult women. 2
Age-Related Considerations for Premenopausal Women
In premenopausal women aged 30-40 years, approximately 17% have ferritin levels <15 μg/L (depleted iron stores), 23% have levels 15-30 μg/L (low iron stores), and 60% have levels >30 μg/L (replete iron stores). 3
Ferritin levels remain relatively stable in women aged 30-40 years, then increase significantly after age 50 (postmenopause), with median values rising from 38 μg/L to 54 μg/L at age 50 and 84 μg/L at age 60. 3
Critical Clinical Thresholds for Interpretation
Ferritin <15 μg/L has 99% specificity for absolute iron deficiency and definitively confirms depleted iron stores. 1, 2
Ferritin levels <30 μg/L generally indicate low body iron stores and warrant clinical attention. 2
Ferritin <45 μg/L provides optimal sensitivity-specificity balance (specificity 0.92) for clinical decision-making regarding iron deficiency. 2
Important Caveats for Clinical Interpretation
Ferritin is an acute-phase protein that rises during inflammation, infection, or tissue damage, potentially masking depleted iron stores even when true iron deficiency exists. 2
In the presence of inflammatory conditions (such as chronic kidney disease, inflammatory bowel disease, or heart failure), the threshold for diagnosing iron deficiency shifts upward to ferritin <100 μg/L. 2
Ferritin should never be interpreted in isolation—always evaluate alongside transferrin saturation (TSAT) and clinical context. 2
The relationship between serum ferritin and stored iron is direct: 1 μg/L of serum ferritin equals approximately 10 mg of stored iron. 2
Common Pitfalls to Avoid
Do not assume that a ferritin value within the "normal range" (20-200 μg/L) excludes iron deficiency—values <30 μg/L indicate low stores despite being technically "normal." 2
Blood donors consistently have lower ferritin levels than non-donors across all age groups, which must be considered when interpreting results. 3
When ferritin is 30-100 μg/L in the context of elevated inflammatory markers (CRP/ESR), a mixed picture of true iron deficiency and anemia of chronic disease may be present. 2