What ferritin level indicates iron deficiency?

Ferritin Levels Indicating Iron Deficiency

In non-inflammatory conditions, serum ferritin <30 μg/L indicates iron deficiency, while in the presence of inflammation, serum ferritin up to 100 μg/L may still be consistent with iron deficiency. 1, 2

Diagnostic Criteria Based on Inflammatory Status

Without Inflammation:

• Ferritin <30 μg/L is the appropriate diagnostic criterion for iron deficiency 1, 2
• This applies to patients without clinical, endoscopic, or biochemical evidence of active inflammatory disease

With Inflammation:

• Ferritin up to 100 μg/L may still indicate iron deficiency 1, 2
• When inflammation is present, using the standard cutoff of 30 μg/L would miss many cases of iron deficiency
• If ferritin is between 30-100 μg/L with inflammation present, a combination of true iron deficiency and anemia of chronic disease is likely 1

Additional Diagnostic Parameters

To improve diagnostic accuracy, especially in cases with borderline ferritin values, consider:

• Transferrin saturation (TSAT):

  • Calculate using: TSAT = (serum iron ÷ total iron binding capacity) × 100
  • TSAT <20% confirms inadequate iron availability for erythropoiesis 2
  • When ferritin >100 μg/L with TSAT <20%, this suggests functional iron deficiency or anemia of inflammation 2

• Other supportive findings of iron deficiency:

  • Low mean corpuscular volume (MCV)
  • Raised red cell distribution width (RDW)
  • Microcytic hypochromic pencil red cells on blood film
  • Low serum iron
  • Raised total iron-binding capacity 1

Recent Evidence and Evolving Perspectives

Recent research suggests that the traditional ferritin cutoffs may be too low:

• A 2022 study found that ferritin levels ≤50 ng/mL may be indicative of early iron deficiency based on soluble transferrin receptor to hepcidin ratio 3
• Some experts argue that current reference ranges lead to underdiagnosis of iron deficiency, particularly in women, and suggest a physiologic ferritin "cutoff" of 50 ng/mL 4

Clinical Implications

• The diagnosis of iron deficiency should always consider the patient's inflammatory status
• In patients with chronic inflammatory conditions (IBD, chronic kidney disease, heart failure, cancer), higher ferritin cutoffs should be used 2
• When ferritin falls in the 30-100 μg/L range, additional testing such as transferrin saturation is particularly valuable to clarify the diagnosis
• Soluble transferrin receptor remains normal in functional iron deficiency but is elevated in true iron deficiency 2

Common Pitfalls to Avoid

• Do not use a single ferritin cutoff for all patients - inflammatory status significantly alters the interpretation
• Do not ignore borderline ferritin values (30-100 μg/L) in patients with inflammatory conditions - these may still represent iron deficiency
• Do not rely solely on ferritin in patients with inflammation - always check transferrin saturation
• Do not miss functional iron deficiency - this occurs when there are adequate iron stores but insufficient iron availability for erythropoiesis

Iron deficiency is a common and treatable condition that significantly impacts quality of life. Using appropriate diagnostic criteria based on inflammatory status is essential for accurate diagnosis and effective treatment.