In CKD, iron deficiency is suggested by which lab values?

• A. TSAT > 50% and ferritin > 1000
• B. TSAT < 5% and ferritin > 1000
• C. TSAT > 30% and ferritin < 100
• D. TSAT < 20% and ferritin < 200

Answer: (D)

Low transferrin saturation with low ferritin best signals iron deficiency in CKD. Transferrin saturation shows how much circulating iron is available for red blood cell production, so a value under 20% indicates insufficient iron in the bloodstream. Ferritin reflects stored iron, and in CKD patients ferritin can rise with inflammation, masking deficiency; when ferritin is still below 200 ng/mL, it means iron stores are depleted. Together, TSAT <20% and ferritin <200 Ng/mL point to true iron deficiency and the need for iron supplementation. The other patterns either show adequate circulating iron, or an inflammatory/redistribution pattern (very high ferritin with low TSAT) that does not reflect true deficiency.