Hematocrit represents the proportion of red blood cells within your total blood volume. This measurement indicates the percentage of blood composed of these oxygen-carrying cells, rather than the liquid plasma or other blood components. Understanding your haematocrit level provides insight into your body’s ability to transport oxygen, which is important for overall health.
Understanding Haematocrit and High Levels
Red blood cells contain hemoglobin, a protein responsible for binding oxygen in the lungs and delivering it throughout the body. A hematocrit test, often part of a complete blood count (CBC), measures this percentage.
For adult men, a healthy haematocrit range is between 40% and 54%, while for adult women, it falls between 36% and 48%. These ranges can vary depending on individual factors and the laboratory conducting the test.
When haematocrit levels are consistently above these normal ranges, it indicates polycythemia or erythrocytosis, an excess of red blood cells in the bloodstream. This surplus of red blood cells can make the blood thicker. Thicker blood can impede efficient blood flow and oxygen delivery to tissues and organs, potentially straining the cardiovascular system.
People with elevated haematocrit may experience symptoms including fatigue, headaches, dizziness, blurred vision, and shortness of breath.
Lifestyle and Environmental Factors
Several non-disease-related factors can contribute to elevated haematocrit levels.
Dehydration occurs when the body lacks sufficient fluid, leading to a temporary reduction in plasma volume. This concentrates the blood, making the percentage of red blood cells appear higher even if the total number of red blood cells has not increased. Addressing fluid intake can often resolve haematocrit elevations caused by dehydration.
Smoking is another lifestyle factor. Carbon monoxide in cigarette smoke binds to hemoglobin, forming carboxyhemoglobin, which reduces the blood’s oxygen-carrying capacity. To compensate, the body produces more red blood cells, stimulated by erythropoietin. Smoking can also decrease plasma volume, further contributing to a higher haematocrit.
Living at high altitudes, where atmospheric oxygen levels are lower, prompts the body to produce more red blood cells. The kidneys detect this reduced oxygen and release more erythropoietin (EPO), which stimulates the bone marrow to increase red blood cell production to enhance oxygen delivery. This is a normal physiological adaptation.
Conditions like sleep apnea, characterized by chronic low oxygen levels during sleep, can also trigger increased red blood cell production as the body attempts to compensate for intermittent oxygen deprivation. Some performance-enhancing drugs, such as anabolic steroids or synthetic erythropoietin injections, directly stimulate red blood cell production, leading to artificially high haematocrit levels.
Underlying Medical Conditions
High haematocrit can also be a sign of underlying medical conditions that affect red blood cell production or oxygenation.
Polycythemia vera (PV) is a rare blood cancer where the bone marrow produces an excessive number of red blood cells, and sometimes white blood cells and platelets. This overproduction often results from a mutation in the JAK2 gene, leading to uncontrolled cell growth.
Chronic lung diseases, such as Chronic Obstructive Pulmonary Disease (COPD) or pulmonary fibrosis, can cause persistently low blood oxygen levels. The body interprets this chronic hypoxia as a need for more oxygen carriers and responds by increasing erythropoietin production, which boosts red blood cell creation. This compensatory mechanism can lead to high haematocrit over time.
Certain kidney conditions may also lead to elevated haematocrit. While kidney disease often causes low erythropoietin and anemia, some kidney disorders or tumors, such as renal cell carcinoma, can inappropriately produce excessive amounts of erythropoietin. This unregulated erythropoietin then overstimulates the bone marrow, resulting in an increased red blood cell count.
Some congenital heart defects can cause blood to bypass the lungs, leading to chronic low oxygen levels. In response, the body produces more red blood cells to enhance its oxygen-carrying capacity. This is a physiological adaptation to improve oxygen delivery.
Importance of Diagnosis and Management
Recognizing high haematocrit levels is important because they can indicate various underlying issues, ranging from lifestyle factors to serious medical conditions.
While temporary elevations due to dehydration might be easily reversible, persistent high levels warrant careful investigation. Consulting a healthcare professional for proper diagnosis is important.
A doctor will order blood tests, including a Complete Blood Count (CBC), to measure haematocrit and other blood components. Further diagnostic tests may be needed to identify the cause of the elevation.
It is important to avoid self-diagnosing or attempting to self-treat, as the appropriate management strategy depends entirely on the identified cause. A healthcare provider can determine the best course of action based on a comprehensive evaluation of the individual’s health status.