Iron Deficiency: Understanding Dangerous Low Iron Levels & Risks

Severity Classification (WHO)

Category	Hemoglobin (g/dL)	Ferritin (ng/mL)
Mild	11–11.9 (W), 11–12.9 (M)	15–30
Moderate	8–10.9	<15
Severe	<8 (W), <8 (M: <13)	<12
Life-Threatening	<7 (W), <8 (M)	—

Severe Anemia Consequences

• High-output heart failure, angina, arrhythmia
• Cerebral hypoxia → confusion, stroke
• Immune impairment
• Pica (ice, clay, dirt)
• In pregnancy: preterm, LBW, maternal mortality

Workup

• CBC, ferritin, iron, TIBC, transferrin saturation, reticulocyte count.
• GI evaluation (EGD/colonoscopy) for occult blood loss in men/postmenopausal women.
• Celiac serology, H. pylori.

Treatment

• Oral iron: Ferrous sulfate 325 mg (65 mg elemental) TID + vitamin C; 3–6 months to replete stores.
• IV iron (ferric carboxymaltose, iron sucrose, ferumoxytol) if: intolerance, malabsorption, severe anemia (Hb<7), active IBD, CKD, need rapid repletion.
• Transfusion only for hemodynamic instability (Hb<7 or symptomatic >7).