From the Guidelines
Elevated hematocrit can result from various causes, including dehydration, polycythemia vera, chronic hypoxic conditions, certain medications, smoking, and genetic disorders, and treatment depends on identifying and addressing the underlying cause. The most common causes of elevated hematocrit include:
- Dehydration, which concentrates the blood
- Polycythemia vera, a bone marrow disorder that leads to excessive production of red blood cells
- Chronic hypoxic conditions such as chronic obstructive pulmonary disease (COPD), sleep apnea, or living at high altitude, which stimulate red blood cell production to compensate for lower oxygen levels
- Certain medications like erythropoietin or anabolic steroids
- Smoking, which can increase carbon monoxide in the blood and stimulate red blood cell production
- Certain genetic disorders, such as high oxygen-affinity hemoglobinopathy or 2,3-diphosphoglycerate mutase deficiency, as noted in 1 Other potential causes include kidney disease, particularly renal cell carcinoma that may produce erythropoietin, and rare conditions like Cushing's syndrome.
According to 1, the diagnosis of polycythemia vera (PV) may be entertained if the hemoglobin/hematocrit level is higher than the 95th percentile of the normal distribution adjusted for sex and race, or if there is a documented increase in the hemoglobin/hematocrit level above the baseline for an individual patient. Additionally, 1 suggests that the measurement of serum EPO and the examination of bone marrow histology can be used to make a working diagnosis of PV.
It is also important to note that certain medications, such as testosterone-replacement therapy, can increase the risk of polycythemia, as mentioned in 1. Therefore, regular monitoring of hematocrit levels is important for patients with chronic conditions that affect red blood cell production, and treatment should be tailored to the underlying cause. In general, treatment may involve hydration, phlebotomy to remove excess blood, oxygen therapy for hypoxic conditions, or specific treatments for underlying disorders, as noted in 1.
From the Research
Causes of Elevated Hematocrit
- Elevated hematocrit can be caused by various conditions, including polycythemia vera (PV) 2, 3, 4, 5
- PV is a myeloproliferative neoplasm characterized by an increased red blood cell mass and increased risk of thrombosis 3
- Other causes of elevated hematocrit include dehydration, smoking, and high altitude 3
- Erythrocytosis (hemoglobin >16.5 mg/dL in men or >16.0 mg/dL in women) is a required diagnostic criterion for PV 3
- Secondary causes of erythrocytosis, such as tobacco smoking or sleep apnea, should be excluded in the diagnosis of PV 3
Risk Factors for Elevated Hematocrit
- Age >60 years and history of thrombosis are risk factors for elevated hematocrit in PV patients 3, 4, 5
- Cardiovascular risk factors and higher absolute neutrophil count are additional predictors for arterial thrombosis in PV patients 5
- JAK2V617F allele burden is a predictor for venous thrombosis in PV patients 5
Clinical Manifestations of Elevated Hematocrit
- Elevated hematocrit can lead to thrombotic complications, such as stroke, myocardial infarction, deep vein thrombosis, and pulmonary embolism 2, 3
- Neurological manifestations, such as transient visual changes, can occur due to impaired capillary blood flow 2, 3
- Bleeding risk is also increased in PV patients, especially in those with acquired von Willebrand disease 3