Is a patient with fatigue and pica, low ferritin (Hypoferritinemia), elevated total iron-binding capacity (TIBC) (Hyper-TIBC-emia), normal hemoglobin (Hgb) level, and iron saturation of 23, iron deficient?

Yes, This Patient Has Iron Deficiency

This patient has functional iron deficiency (iron-deficient erythropoiesis) despite the seemingly "normal" ferritin of 17 ng/mL, as evidenced by the elevated TIBC (410 mg/dL) and borderline-low transferrin saturation (23%). The combination of pica (a classic symptom of iron deficiency) and fatigue with these laboratory findings confirms the diagnosis, even with normal hemoglobin 1.

Understanding the Laboratory Pattern

Your patient's labs reveal a classic pattern of early iron deficiency:

• Ferritin 17 ng/mL: This is definitively low. While the threshold varies by context, ferritin <30 ng/mL confirms absolute iron deficiency in individuals without inflammation 1, 2. In apparently healthy adults, ferritin <15-20 ng/mL is diagnostic 3.

• TIBC 410 mg/dL (elevated): The elevated TIBC indicates the body is attempting to capture more iron by producing more transferrin (iron-binding protein). This is a compensatory response to iron depletion 1, 4.

• Transferrin saturation 23%: While technically above the classic 20% threshold, this is borderline and must be interpreted in context. The calculation is: (Iron 96 ÷ TIBC 410) × 100 = 23.4% 1. In the presence of low ferritin and elevated TIBC, this represents inadequate iron availability for erythropoiesis 1.

• Normal hemoglobin: Iron deficiency progresses through stages. Your patient is in Stage 2 (iron-deficient erythropoiesis without anemia)—iron stores are depleted (low ferritin), but hemoglobin hasn't dropped yet 2, 4. Pica often appears before anemia develops 2.

Why This Is Iron Deficiency

The ferritin test is highly specific (92-98%) for iron deficiency when low 3. At 17 ng/mL, there is no ambiguity—this patient has depleted iron stores 1, 2. The elevated TIBC (normal range typically 240-450 mg/dL, with values >400 mg/dL indicating significant iron depletion) confirms the body is desperately trying to bind any available iron 4.

Key diagnostic principle: Ferritin <30 ng/mL with elevated TIBC confirms absolute iron deficiency regardless of other parameters 1, 4. The transferrin saturation of 23%, while not severely low, is insufficient when iron stores are this depleted 1.

Clinical Significance of Pica

Pica (craving non-food items like ice, dirt, or starch) is a pathognomonic symptom of iron deficiency and often appears before anemia develops 2. Its presence with low ferritin makes the diagnosis certain, even without anemia 2.

Diagnostic Pitfalls to Avoid

• Don't wait for anemia to develop: Iron deficiency causes symptoms (fatigue, pica, restless legs) before hemoglobin drops 2, 4. Treating at this stage prevents progression to anemia.

• Don't be falsely reassured by "borderline" saturation: A saturation of 23% in the context of ferritin 17 ng/mL still represents iron-deficient erythropoiesis 1, 4. The saturation would need to be >30-50% to indicate truly adequate iron availability 1.

• Don't ignore elevated TIBC: TIBC >400 mg/dL is a red flag for iron depletion and supports the diagnosis when ferritin is borderline 4.

Mandatory Next Steps

1. Identify the source of iron loss: In adult men and postmenopausal women, gastrointestinal evaluation (starting with colonoscopy if age >50) is mandatory to exclude malignancy 1, 2. In premenopausal women, menstrual blood loss is the most common cause, but GI evaluation is still warranted if symptoms are severe or refractory 2.

2. Initiate iron replacement:

   • Oral iron (ferrous sulfate 325 mg daily, containing 65 mg elemental iron) is first-line 2
   • Recheck hemoglobin in 4 weeks—expect a 1-2 g/dL increase if compliant and absorbing 2
   • If no response, consider malabsorption, ongoing blood loss, or need for IV iron 1, 2

3. Monitor response: Recheck CBC and iron parameters (ferritin, TSAT) at 4-8 weeks 1. Target ferritin >50 ng/mL and TSAT >20% to ensure adequate repletion 1.

Why the Numbers Don't Contradict Iron Deficiency

The iron level of 96 mcg/dL (normal range typically 60-170 mcg/dL) may seem reassuring, but serum iron has significant diurnal variation and is affected by recent meals 1. It is the least reliable single parameter for diagnosing iron deficiency 4. The combination of low ferritin + elevated TIBC is far more diagnostic than serum iron alone 4.

Bottom line: Ferritin 17 ng/mL is the most important finding here. It definitively confirms depleted iron stores 3, 4. The elevated TIBC and clinical symptoms (pica, fatigue) support this diagnosis. Treat now to prevent progression to overt anemia 2.