What does a ferritin level of 55 indicate in an adult?

What Does a Ferritin of 55 Indicate?

A ferritin level of 55 μg/L falls in the borderline zone where iron stores are likely adequate in most adults, but this value does not definitively exclude iron deficiency, particularly in the presence of inflammation or chronic disease. 1

Interpretation Framework

In Apparently Healthy Adults

• For men: A ferritin of 55 μg/L is below the average of 135 μg/L but above the deficiency threshold, suggesting reduced but not depleted iron stores 2
• For women: This level is above the average of 43 μg/L, indicating adequate iron stores in most cases 2
• A ferritin threshold of <45 μg/L has 85% sensitivity and 92% specificity for iron deficiency, meaning your level of 55 μg/L makes true iron deficiency less likely but not impossible 1

Critical Context: The Inflammation Factor

Ferritin is an acute-phase reactant that rises during inflammation, infection, or tissue damage, potentially masking underlying iron deficiency. 1, 2 This is the most important caveat when interpreting a ferritin of 55 μg/L.

• In patients with chronic inflammatory conditions (inflammatory bowel disease, chronic kidney disease, rheumatoid arthritis, heart failure), iron deficiency may be present even with ferritin levels of 50-100 μg/L 2
• Research demonstrates that ferritin levels >50 μg/L can still be consistent with iron deficiency when inflammation is present 3
• If inflammation is suspected, check C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR) to determine if ferritin is falsely elevated 2

Complementary Testing Required

Ferritin alone provides an incomplete picture—you must calculate transferrin saturation (TSAT) to assess iron availability for red blood cell production. 1, 2

Calculate TSAT Using This Formula:

• TSAT = (serum iron × 100) ÷ total iron-binding capacity 2
• If TSAT <20%: This indicates functional iron deficiency despite the ferritin of 55 μg/L, meaning insufficient iron is available for erythropoiesis 1, 2
• If TSAT ≥20%: Iron availability is adequate 1

Clinical Decision Algorithm

If No Inflammation Present (Normal CRP/ESR):

• Ferritin 55 μg/L with TSAT ≥20% → Iron stores are adequate; no intervention needed 2
• Ferritin 55 μg/L with TSAT <20% → Functional iron deficiency; consider iron supplementation 2

If Inflammation Present (Elevated CRP/ESR):

• Ferritin 55 μg/L may represent mixed iron deficiency (both absolute and functional) 2
• TSAT <16-20% confirms iron deficiency requiring treatment despite the ferritin level 2
• Consider soluble transferrin receptor (sTfR) testing if ferritin and TSAT are discordant—elevated sTfR confirms true iron deficiency even with inflammation 2

In Chronic Kidney Disease Patients:

• Ferritin <100 ng/mL combined with TSAT <20% defines absolute iron deficiency in this population 2
• Your level of 55 μg/L would warrant iron supplementation if TSAT is also low 2

Common Pitfalls to Avoid

• Do not assume ferritin 55 μg/L excludes iron deficiency without checking TSAT 2, 3
• Do not ignore symptoms of iron deficiency (fatigue, reduced exercise tolerance) even when ferritin appears borderline normal 2
• Do not overlook celiac disease, which is present in 3-5% of iron deficiency cases and can cause persistently low-normal ferritin 2
• Do not continue investigating for iron overload—ferritin must exceed 150 μg/L before considering this diagnosis, and levels >1000 μg/L are typically required for true overload concerns 2, 4

When to Act on a Ferritin of 55 μg/L

Initiate iron supplementation if: 2

• TSAT <20% (regardless of ferritin level)
• Patient has symptoms of iron deficiency (fatigue, reduced exercise capacity)
• Patient belongs to high-risk groups (menstruating females, vegetarians/vegans, athletes, regular blood donors)
• Chronic inflammatory condition is present with TSAT <20%

No intervention needed if: 2

• TSAT ≥20% and patient is asymptomatic
• No chronic disease or inflammation present
• Hemoglobin is normal and stable