Hemoglobin (Hb) is a protein found inside red blood cells, and its function is to carry oxygen from the lungs to all other tissues and organs in the body. When laboratory tests indicate a high concentration of hemoglobin, this condition is medically referred to as erythrocytosis, or polycythemia. Elevated hemoglobin levels cause the blood to become thicker, a state known as hyperviscosity. This increased thickness forces the heart to work harder to pump blood and raises the risk of blood flow complications.
Recognizing the Signs of Elevated Hemoglobin
Physical manifestations of elevated hemoglobin often arise from the blood’s increased viscosity, which slows circulation. Individuals may experience neurological symptoms such as persistent headaches, dizziness, or a sensation of ringing in the ears, known as tinnitus. Visual disturbances, including blurred or double vision, can also occur due to poor blood flow in the small vessels of the eyes.
Circulatory signs are frequently visible, presenting as a flushing or redness, particularly on the face, palms, and soles of the feet. This ruddy complexion is a direct result of the high concentration of oxygen-carrying cells near the skin’s surface. General symptoms of poor oxygen delivery or increased cardiac strain include unexplained fatigue and shortness of breath, especially during physical activity.
Lifestyle and Environmental Contributors
One of the most common non-pathological reasons for elevated hemoglobin is living at high altitudes, typically above 6,000 to 8,000 feet. The air at these elevations contains less oxygen, creating a state of chronic hypoxia in the body. In response, the kidneys release the hormone erythropoietin (EPO), which stimulates the bone marrow to produce more red blood cells and, consequently, more hemoglobin.
Habits like smoking or chronic vaping also contribute significantly to higher hemoglobin levels due to exposure to carbon monoxide. When inhaled, carbon monoxide binds to hemoglobin with an affinity 200 times greater than oxygen, effectively blocking oxygen transport. The body misinterprets this as a lack of oxygen and compensates by increasing the total number of red blood cells to overcome the deficit.
Dehydration, although temporary, causes a relative increase in hemoglobin concentration known as hemoconcentration. When the volume of the plasma component of blood decreases, the red blood cells become more concentrated, artificially raising the measured hemoglobin value. This condition is quickly reversible with adequate fluid intake.
The use of certain pharmaceutical agents or performance-enhancing substances can also directly stimulate erythropoiesis. Exogenous testosterone therapy, often used for hormone replacement, is known to increase EPO production and elevate red blood cell mass. Similarly, the misuse of recombinant human erythropoietin (r-HuEPO), a drug used to treat anemia, directly forces the bone marrow to overproduce red blood cells.
Underlying Medical Conditions
When elevated hemoglobin is not attributable to lifestyle factors, it often points to a more serious underlying medical condition, categorized as primary or secondary erythrocytosis. Secondary erythrocytosis is the most common pathological cause, arising when the body increases red blood cell production in response to chronic low blood oxygen. Chronic lung diseases, such as severe Chronic Obstructive Pulmonary Disease (COPD) or pulmonary fibrosis, lead to inefficient gas exchange, causing persistent hypoxia.
Severe obstructive sleep apnea causes repeated, brief episodes of low blood oxygen saturation during sleep, which also triggers EPO release. Kidney conditions can also lead to the inappropriate and excessive secretion of EPO, even when oxygen levels are normal. Certain benign kidney cysts or tumors can produce EPO independently of the body’s oxygen demands.
Primary erythrocytosis, most notably Polycythemia Vera (PV), is a distinct disorder originating in the bone marrow itself. In PV, the bone marrow stem cells produce an excessive amount of red blood cells, often alongside other blood components, regardless of EPO levels. This condition is frequently linked to a mutation in the Janus kinase 2 (JAK2) gene, which allows the marrow cells to grow and divide independently. Both primary and secondary erythrocytosis significantly increase the risk of life-threatening blood clots due to the excessive number of cells slowing blood flow.
Diagnosis and Management Approaches
A doctor typically identifies an elevated hemoglobin level through a routine Complete Blood Count (CBC) blood test. Once high levels are confirmed, the diagnostic process focuses on determining the specific cause through further specialized testing. Measuring the level of erythropoietin (EPO) in the blood is a standard next step.
Low EPO levels often suggest a primary bone marrow disorder like Polycythemia Vera (PV), while high EPO levels point toward a secondary cause like chronic hypoxia or inappropriate kidney stimulation. Genetic testing for the JAK2 mutation is a definitive way to confirm a PV diagnosis.
Management strategies are highly individualized and depend entirely on the root cause of the elevated hemoglobin. For relative polycythemia caused by dehydration, simple rehydration with intravenous or oral fluids is the standard intervention.
If the cause is related to chronic low oxygen, treating the underlying condition, such as using continuous positive airway pressure (CPAP) for sleep apnea or oxygen therapy for COPD, is necessary. For conditions like Polycythemia Vera or very high secondary erythrocytosis, therapeutic phlebotomy is a common treatment, involving the removal of a unit of blood to physically reduce the red cell volume. Low-dose aspirin is also often prescribed to reduce the risk of blood clot formation associated with the increased viscosity.