Differential Diagnosis for Increased Haemoglobin and RBC Count

Single Most Likely Diagnosis

• Dehydration: This is often the most common cause of increased haemoglobin and RBC count due to a decrease in plasma volume, which concentrates the blood cells.

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. It's a common cause of increased haemoglobin and RBC count.
• Smoking: Chronic smoking can lead to increased carboxyhemoglobin levels, which may stimulate erythropoietin production and increase RBC count.

Do Not Miss Diagnoses

• Renal Cell Carcinoma: Some renal cell carcinomas can produce erythropoietin, leading to increased RBC production. Missing this diagnosis could be fatal due to the potential for metastasis.
• Testicular Cancer: Certain testicular tumors can also produce human chorionic gonadotropin (hCG), which can stimulate erythropoietin production, leading to increased RBC count.
• Cerebellar Hemangioblastoma: These tumors can produce erythropoietin, leading to secondary polycythemia. Early diagnosis is crucial for effective treatment.

Rare Diagnoses

• Erythropoietin-Producing Tumors: Rare tumors such as hepatocellular carcinoma, phaeochromocytoma, or uterine fibroids can produce erythropoietin, leading to increased RBC count.
• Androgen Abuse: The use of anabolic steroids can stimulate erythropoietin production and increase RBC count.
• High-Altitude Adaptation: People living at high altitudes for extended periods can develop increased RBC count as an adaptation to the lower oxygen levels.