Differential Diagnosis for Mildly High HGB, MCH, MCHC

Single Most Likely Diagnosis

• Dehydration: This is often the most common and straightforward reason for mildly elevated hemoglobin (HGB), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC) levels. Dehydration reduces plasma volume, which in turn concentrates the blood components, leading to elevated values without an actual increase in red blood cell mass.

Other Likely Diagnoses

• Smoking: Smoking can increase HGB levels due to the body's attempt to compensate for the decreased oxygen-carrying capacity of the blood caused by carbon monoxide from cigarette smoke.
• High Altitude: Living at high altitudes can lead to increased HGB levels as the body adapts to lower oxygen levels by producing more red blood cells.
• Polycythemia Vera: A myeloproliferative disorder that leads to an overproduction of red blood cells, white blood cells, and platelets. It can cause elevated HGB, MCH, and MCHC, though it's less common than other causes.

Do Not Miss Diagnoses

• Chronic Lung Disease: Conditions like chronic obstructive pulmonary disease (COPD) can lead to hypoxia, prompting the body to increase red blood cell production, which in turn can elevate HGB, MCH, and MCHC.
• Sleep Apnea: Severe sleep apnea can cause intermittent hypoxia, leading to increased erythropoietin production and subsequently elevated red blood cell indices.
• Carbon Monoxide Poisoning: Chronic exposure to carbon monoxide can lead to increased HGB levels due to the displacement of oxygen from hemoglobin, though this would typically be identified through other means.

Rare Diagnoses

• Erythrocytosis due to EPO Abuse: Athletes may misuse erythropoietin (EPO) to enhance performance, leading to increased red blood cell production and elevated HGB, MCH, and MCHC levels.
• Congenital Methemoglobinemia: A rare condition that affects the hemoglobin's ability to bind oxygen, potentially leading to elevated MCH and MCHC due to the presence of methemoglobin.
• Other Myeloproliferative Neoplasms: Besides polycythemia vera, other myeloproliferative disorders can occasionally present with elevated red blood cell indices, though this is less common.