Do I have iron deficiency anemia?

Diagnosing Iron Deficiency

You need laboratory confirmation with serum ferritin and/or transferrin saturation to determine if you have iron deficiency—clinical suspicion alone is insufficient for diagnosis. 1

Key Diagnostic Tests

Serum ferritin is the single most powerful and specific test for iron deficiency. 1 Here's how to interpret it:

• Ferritin <15 μg/L: Highly specific for iron deficiency (99% specificity), diagnostic of absent iron stores 1
• Ferritin <30 μg/L: Generally indicates low body iron stores 1
• Ferritin <45 μg/L: Optimal cutoff when inflammation is present (92% specificity) 1
• Ferritin >100-150 μg/L: Iron deficiency is almost certainly not present, even with inflammation 1

Important Caveat About Ferritin

Ferritin is an acute phase protein that can be falsely elevated by inflammation, malignancy, liver disease, or chronic conditions. 1 In these situations, a "normal" ferritin (12-100 μg/L) may mask true iron deficiency. 1

Additional Confirmatory Tests

If ferritin results are equivocal or you have chronic inflammatory conditions:

• Transferrin saturation <20-30%: Supports iron deficiency diagnosis 1, 2
• Mean cell volume (MCV): Microcytosis (low MCV) is characteristic but may be absent with concurrent folate/B12 deficiency 1
• Mean cell hemoglobin (MCH): May be more reliable than MCV and less machine-dependent 1

Therapeutic Trial as Diagnostic Tool

A hemoglobin rise ≥10 g/L within 2 weeks of iron therapy is highly suggestive of absolute iron deficiency, even if iron studies are equivocal. 1 This response to a 3-week trial of oral iron can confirm true deficiency when laboratory tests are unclear. 1

What You Need Before Diagnosis

To confirm iron deficiency anemia specifically, you need:

1. Anemia confirmed: Hemoglobin below normal range for your age/sex (men <130 g/L, non-pregnant women <120 g/L per WHO criteria) 1
2. Iron deficiency confirmed: Low ferritin and/or low transferrin saturation 1, 2

Note that you can have iron deficiency without anemia (non-anemic iron deficiency), which still requires investigation in men, postmenopausal women, or those with GI symptoms. 1

Common Diagnostic Pitfalls

• Don't assume microcytosis equals iron deficiency: Thalassemia, sideroblastic anemia, and chronic disease can also cause microcytosis 1
• Don't rely on hemoglobin alone: It's a late indicator with low sensitivity and specificity 1, 3
• Don't skip iron studies in inflammatory conditions: Use higher ferritin cutoffs (45 μg/L) and consider transferrin saturation 1

Bottom line: Get blood work including complete blood count, serum ferritin, and ideally transferrin saturation to definitively answer whether you have iron deficiency. 1, 2