Hematocrit (Hct) measures the percentage of red blood cells (RBCs) within the total volume of your blood. These cells contain hemoglobin, the protein responsible for transporting oxygen from the lungs to all body tissues. When this percentage is elevated, the condition is known as erythrocytosis or polycythemia, which causes the blood to become thicker. This increased viscosity slows blood flow, forcing the heart to work harder and raising the risk of complications like blood clots, heart attack, and stroke. A medical professional must always investigate elevated Hct to determine the underlying cause before any reduction strategy is implemented.
Understanding the Causes of Elevated Hematocrit
The approach to reducing Hct depends on whether the concentration is apparent or actual. An apparent rise, termed relative polycythemia, occurs when plasma volume decreases without a corresponding loss of red blood cells. Severe dehydration, excessive diuretic use, or persistent vomiting can concentrate the blood, leading to a falsely high Hct reading. Addressing the fluid imbalance rapidly corrects this type of elevation.
The more serious scenario is absolute polycythemia, which reflects a true increase in the total red blood cell mass. This is categorized as primary or secondary. Primary polycythemia, such as Polycythemia Vera, is a rare disorder originating in the bone marrow due to a genetic mutation (often JAK2), causing uncontrolled RBC production.
Secondary polycythemia is the body’s response to chronic tissue oxygen deprivation, known as hypoxia. Conditions that impair oxygen transfer, like severe lung disease, obstructive sleep apnea, or living at high altitudes, trigger the kidneys to release more erythropoietin (EPO). EPO stimulates the bone marrow to produce more red blood cells to compensate for low oxygen levels. Certain tumors or the use of performance-enhancing substances can also lead to secondary polycythemia by increasing EPO levels.
Lifestyle Modifications for Natural Reduction
The initial step often involves making changes to counteract common causes like dehydration and chronic hypoxia. Increasing daily water intake is the most effective way to lower Hct levels associated with relative polycythemia. Hydration dilutes the blood, restoring plasma volume and bringing the red blood cell percentage back into a normal range. Avoiding excessive consumption of diuretic substances like alcohol and caffeine also prevents fluid loss that concentrates the blood.
Quitting smoking is a powerful intervention for reducing Hct driven by secondary polycythemia. Carbon monoxide from cigarette smoke binds to hemoglobin, reducing the blood’s oxygen-carrying capacity. The body interprets this as chronic oxygen starvation and responds by producing more red blood cells, driving up the Hct level. Eliminating tobacco use removes this stimulus, allowing RBC production to normalize over time.
Dietary adjustments are supportive, especially if high Hct is accompanied by elevated iron stores. Since iron is essential for red blood cell production, limiting the intake of iron-rich foods, such as red meat, and avoiding unnecessary iron supplements can slow erythropoiesis.
Managing underlying conditions that cause chronic hypoxia is another non-medical strategy. Individuals with obstructive sleep apnea should consistently use a Continuous Positive Airway Pressure (CPAP) machine to ensure adequate nighttime oxygenation. If high Hct is linked to altitude, spending regular periods at lower elevations can reduce the hypoxic drive that forces the body to create excess red blood cells.
Clinical Treatments and Monitoring
When lifestyle changes are insufficient or a diagnosed blood disorder is the cause, medical intervention is necessary to safely lower Hct. The most common and direct treatment is therapeutic phlebotomy, a procedure identical to blood donation where a controlled volume of blood (typically 350 to 500 mL) is drawn. This physically reduces the total red blood cell mass and blood viscosity, providing rapid symptom relief and lowering the risk of thrombosis.
For conditions like Polycythemia Vera (PV), the goal of phlebotomy is to maintain hematocrit below 45% in men and 42% in women to reduce the incidence of blood clots. Patients with PV are also prescribed a daily low-dose aspirin regimen to inhibit platelet aggregation and minimize clot risk.
If phlebotomy alone cannot control Hct, or if a patient is high-risk for complications, pharmacological agents are introduced. Cytoreductive medications, such as hydroxyurea, suppress bone marrow function to decrease red blood cell production. Other options, including interferon-alpha or ruxolitinib, may be used as alternatives, often targeting specific genetic pathways involved in the disease.
Regular medical monitoring is required for anyone managing elevated Hct. This involves periodic complete blood counts to ensure Hct levels remain within the therapeutic target range. Physician supervision is necessary to adjust treatment, manage medication side effects, and prevent complications like iron deficiency from frequent phlebotomy.