Iron-Deficiency Anemia

The most common anemia worldwide hides behind vague fatigue — but one lab pattern and a handful of physical findings tell you exactly what's happening before the hemoglobin even drops.

Iron deficiency anemia (IDA) results from inadequate iron to support erythropoiesis, producing small, pale red blood cells. The classic lab signature is microcytic, hypochromic anemia: low MCV (<80 fL), low serum iron, low ferritin (the most sensitive early marker, <12 ng/mL), and elevated TIBC (the body reaching for iron it doesn't have). Hemoglobin and hematocrit drop later. Common causes include chronic blood loss (heavy menses, GI bleeding — always think occult GI loss in older adults or males), inadequate dietary intake, and increased demand (pregnancy, rapid growth in children). Assessment findings beyond fatigue include pallor, tachycardia, exertional dyspnea, pica (craving ice or dirt), brittle spoon-shaped nails (koilonychia), and glossitis. Nursing priorities center on oral iron supplementation: give on an empty stomach with vitamin C to enhance absorption, avoid giving with calcium, antacids, or dairy which inhibit absorption. Administer liquid iron through a straw to prevent tooth staining. Expect stools to turn black/tarry — this is expected, not GI bleeding. IV iron (iron dextran, ferric carboxymaltose) may be used when oral iron is not tolerated; iron dextran requires a test dose and anaphylaxis monitoring, while newer formulations such as ferric carboxymaltose do not require a test dose. Dietary teaching emphasizes heme iron sources (red meat, organ meats) over non-heme sources (spinach, beans) because heme iron absorbs more efficiently.

Key Distinctions

Don't confuse IDA's low ferritin and high TIBC with anemia of chronic disease, which shows low iron but normal-to-high ferritin and low TIBC (the body has iron but can't use it). Students mix up black stools from iron supplements with melena from GI bleeding — iron stools are expected and non-emergent. IDA is microcytic (low MCV); B12 and folate deficiency anemias are macrocytic (high MCV) — the MCV is your sorting tool.

Clinical Pearl

Ferritin falls first, hemoglobin falls last. If ferritin is low and TIBC is high, the body is iron-starved — don't wait for the H&H to catch up.