From the Guidelines
Elevated hemoglobin and hematocrit levels are a significant concern and require immediate medical attention if they exceed 20 g/dL and 65%, respectively, and are associated with symptoms of hyperviscosity, as indicated by the ACC/AHA 2008 guidelines 1. High hemoglobin and hematocrit levels indicate an increased concentration of red blood cells in your blood, a condition known as polycythemia or erythrocytosis. Normal hemoglobin ranges are typically 13.5-17.5 g/dL for men and 12.0-15.5 g/dL for women, while normal hematocrit ranges are 41-50% for men and 36-48% for women.
Causes and Risks
Elevated levels can be caused by dehydration (relative polycythemia), which is temporary and resolves with proper hydration. More concerning causes include:
- Chronic lung disease
- Heart conditions
- Living at high altitude
- Smoking
- Polycythemia vera (a bone marrow disorder) These elevated levels make blood thicker, increasing the risk of:
- Blood clots
- Stroke
- Heart problems
Diagnosis and Treatment
If you have high levels, drink plenty of water and see your doctor for proper evaluation. Treatment depends on the underlying cause and may include:
- Lifestyle changes
- Phlebotomy (blood removal)
- Medications to reduce red blood cell production Your doctor will likely order additional tests to determine the cause, including:
- Oxygen levels
- Kidney function tests
- Possibly genetic testing Therapeutic phlebotomy is usually unnecessary unless the hemoglobin is more than 20 g/dL and the hematocrit is greater than 65% with associated symptoms of hyperviscosity and no evidence of dehydration, as stated in the ACC/AHA 2008 guidelines 1. It is essential to note that repetitive phlebotomies can deplete iron stores and may result in production of iron-deficient red blood cells, which is undesirable due to the reduced oxygen-carrying capacity and deformability of red blood cells (microcytes) and increased risk of stroke, as mentioned in the study 1.
From the Research
Significance of Elevated Hemoglobin (Hb) and Hematocrit (Hct) Levels
Elevated Hemoglobin (Hb) and Hematocrit (Hct) levels are significant indicators of various health conditions. The key points to consider are:
- Elevated Hb and Hct levels can be evidence of polycythemia rubra vera, a myeloproliferative neoplasm characterized by unregulated red blood cell production 2, 3, 4, 5
- However, erythrocytosis is more commonly due to an underlying non-hematological disease, and a secondary polyglobulia must be excluded to establish the diagnosis of polycythemia 4
- Patients with elevated Hb and Hct levels are at risk of thrombosis, both venous and arterial, and may experience symptoms such as fatigue, pruritus, and painful splenomegaly 2, 3, 5
- The World Health Organization's major diagnostic criteria for polycythemia vera include an elevated Hb or Hct level, abnormal results on bone marrow biopsy, and presence of the Janus kinase 2 genetic mutation 3, 5
- Elevated Hb and Hct levels can also be associated with macrocytosis, which can contribute to elevated Hb and Hct levels and mimic a diagnosis of polycythemia vera 6
Diagnostic Considerations
When evaluating elevated Hb and Hct levels, the following diagnostic considerations are important:
- A bone marrow aspiration, cytological examination, and molecular genetic testing may be necessary to confirm the diagnosis of polycythemia vera 4
- Serum erythropoietin (EPO) level can help distinguish primary and secondary polycythemia, but further testing such as the JAK-2 gene mutation test may be necessary 3
- The mean corpuscular volume (MCV) should be assessed in patients with elevated Hb and Hct levels, as macrocytosis can contribute to elevated Hb and Hct levels and mimic a diagnosis of polycythemia vera 6
Treatment and Management
The treatment and management of elevated Hb and Hct levels depend on the underlying cause. Key points to consider are:
- Phlebotomy is a primary treatment for polycythemia vera, with a target Hct level of less than 45% to reduce thrombotic events 2, 5
- Low-dose aspirin and cytoreductive therapy, such as hydroxyurea, may be added to reduce thrombotic events and improve quality of life 2, 5
- Smoking cessation and addressing cardiometabolic disease are important modifiable risk factors to reduce the risk of thrombosis 5