Differential Diagnosis for Elevated RBC, HGB, HCT

Single Most Likely Diagnosis

• Dehydration: This is often the most common cause of elevated red blood cell (RBC) count, hemoglobin (HGB), and hematocrit (HCT) due to a reduction in plasma volume, which concentrates the blood components.

Other Likely Diagnoses

• Chronic Hypoxia: Conditions such as chronic obstructive pulmonary disease (COPD), sleep apnea, or living at high altitudes can lead to increased erythropoietin production, stimulating the bone marrow to produce more RBCs.
• Polycythemia Vera: A myeloproliferative disorder characterized by the overproduction of RBCs, white blood cells, and platelets, often presenting with elevated HGB and HCT.
• Smoking: Chronic smoking can lead to increased carboxyhemoglobin levels, which may falsely elevate HGB and HCT measurements, and also stimulate erythropoiesis due to chronic hypoxia.

Do Not Miss Diagnoses

• Renal Cell Carcinoma: Some renal cell carcinomas can produce erythropoietin, leading to secondary polycythemia.
• Testosterone Replacement Therapy: Exogenous testosterone can stimulate erythropoiesis, leading to elevated RBC, HGB, and HCT.
• Carbon Monoxide Poisoning: Chronic exposure to carbon monoxide can lead to increased carboxyhemoglobin, which may cause a relative polycythemia.

Rare Diagnoses

• Erythropoietin-Producing Tumors: Rare tumors such as hepatocellular carcinoma, uterine fibroids, or cerebellar hemangioblastomas can produce erythropoietin, leading to elevated RBC, HGB, and HCT.
• Congenital Methemoglobinemia: A rare condition that affects the production of hemoglobin, potentially leading to elevated HGB measurements due to the presence of methemoglobin.
• High-Altitude Adaptation: Individuals living at very high altitudes may develop physiological adaptations that include increased RBC production to compensate for lower oxygen levels.