Understanding high hemoglobin
Hemoglobin is an iron-rich protein in red blood cells that transports oxygen throughout the body. A high hemoglobin count, also known as polycythemia or erythrocytosis, means your blood contains a higher-than-normal amount of this protein. This can cause the blood to become thicker and less able to flow smoothly, which poses significant health risks.
Identifying the cause of a high hemoglobin level is the critical first step in management. While some causes are relatively benign and easily addressed, others, like polycythemia vera, require ongoing medical care.
Polycythemia vera: The primary cause
Polycythemia vera (PV) is the classic answer to the question, "what disease has high hemoglobin?". It is a rare, slow-growing type of blood cancer originating in the bone marrow, where blood cells are produced.
What happens in polycythemia vera?
- Overproduction of blood cells: In PV, the bone marrow produces an excess of red blood cells. In many cases, it also produces too many white blood cells and platelets.
- Genetic mutation: This overproduction is most often caused by a mutation in the JAK2 gene, which makes blood-producing stem cells grow and divide uncontrollably.
- Increased blood viscosity: The proliferation of red blood cells makes the blood thicker (more viscous), which slows circulation.
Key symptoms of PV
Many people with PV have no noticeable symptoms, and the condition is often discovered during a routine blood test. When symptoms do occur, they can include:
- Headaches, dizziness, or blurred vision
- Fatigue and weakness
- Itchiness, especially after a warm bath or shower
- Reddened skin (plethora), particularly on the face
- Numbness, tingling, or burning sensations in the hands or feet (erythromelalgia)
- A feeling of fullness or pain in the upper left abdomen due to an enlarged spleen (splenomegaly)
Secondary polycythemia: Responding to low oxygen
Unlike PV, secondary polycythemia is not a cancer but an excessive red blood cell production caused by an underlying condition that leads to chronically low oxygen levels. The body compensates for this oxygen deprivation by producing more erythropoietin (EPO), a hormone that stimulates red blood cell production.
Medical conditions causing secondary polycythemia
- Lung diseases: Chronic obstructive pulmonary disease (COPD), emphysema, and pulmonary fibrosis can impair the lungs' ability to transfer oxygen, leading to persistent hypoxia.
- Heart conditions: Congenital heart defects or other severe heart diseases can cause inadequate oxygen circulation.
- Kidney tumors: In rare cases, tumors in the kidney can secrete EPO directly, leading to an overproduction of red blood cells.
- Sleep apnea: Obstructive sleep apnea can cause intermittent periods of hypoxia during sleep, prompting the body to produce more red blood cells.
- High-affinity hemoglobin: This is a rare genetic condition where a type of abnormal hemoglobin binds to oxygen so tightly that it is not released to the body's tissues.
Non-medical and environmental factors
Sometimes, a high hemoglobin count is not caused by a disease but by environmental or lifestyle factors. These can lead to a condition known as relative polycythemia, where the red blood cell count appears high due to a reduction in plasma volume, or a mild absolute increase.
- Living at high altitude: Lower oxygen levels at high altitudes naturally cause the body to produce more hemoglobin to compensate.
- Smoking: The carbon monoxide in cigarette smoke decreases the oxygen-carrying capacity of the blood, so the body makes more hemoglobin to compensate.
- Severe dehydration: Loss of body fluid from severe vomiting or diarrhea concentrates the blood, causing hemoglobin levels to appear artificially high.
- Medications: Certain drugs, including anabolic steroids and testosterone replacement therapy, can increase red blood cell production.
Comparison of polycythemia vera vs. secondary polycythemia
| Feature | Polycythemia Vera (Primary) | Secondary Polycythemia |
|---|---|---|
| Underlying Cause | A rare acquired genetic mutation, most commonly in the JAK2 gene, causing autonomous overproduction in the bone marrow. | Response to an underlying condition causing chronic hypoxia or excess EPO production. |
| Erythropoietin (EPO) Levels | Low or below-normal, because the bone marrow is overproducing red blood cells independently of EPO. | High, as the body produces more EPO in an effort to correct low oxygen levels. |
| Other Blood Counts | Often associated with an increase in white blood cells and platelets as well (panmyelosis). | Typically, only the red blood cell count is elevated. |
| Spleen Size | An enlarged spleen (splenomegaly) is a common finding. | Splenomegaly is generally not present, unless related to the underlying condition. |
| Treatment Focus | Reducing blood viscosity and suppressing bone marrow production via phlebotomy and medication. | Addressing the underlying cause, such as treating lung disease or using CPAP for sleep apnea. |
Diagnosis and treatment
If a routine complete blood count (CBC) test reveals a high hemoglobin level, a doctor will perform further tests to determine the exact cause. These can include:
- Physical examination to check for an enlarged spleen or other symptoms.
- Blood tests to measure erythropoietin (EPO) levels.
- Genetic testing for the JAK2 mutation to confirm or rule out PV.
- Bone marrow biopsy to examine the blood-producing cells.
- Imaging studies to check for kidney tumors or heart conditions.
Treatment depends on the cause of the high hemoglobin count. For PV, treatment may involve therapeutic phlebotomy (removal of blood) to reduce red blood cell mass, or medication to suppress bone marrow activity and prevent blood clots. For secondary polycythemia, managing the underlying condition is the primary goal. This might include oxygen therapy for lung disease or quitting smoking.
When to see a doctor
While some factors can temporarily elevate hemoglobin levels, persistent or significantly high readings should be evaluated by a healthcare professional. You should seek medical attention if you experience symptoms associated with high hemoglobin, such as:
- Frequent headaches or dizziness
- Fatigue or shortness of breath
- Itchiness after bathing
- Numbness or tingling in the hands or feet
- Unexplained bruising or bleeding
For more detailed medical information on polycythemia vera and other blood cancers, consult authoritative resources like the National Cancer Institute or the Leukemia and Lymphoma Society.
Conclusion
A high hemoglobin count can result from a variety of causes, ranging from simple dehydration to a serious blood cancer like polycythemia vera. Distinguishing between primary and secondary causes is critical for proper diagnosis and effective treatment. While lifestyle changes can address some factors, persistent elevation requires medical evaluation to prevent potentially life-threatening complications like blood clots, heart attacks, and strokes. Accurate diagnosis is the most important step toward successful management and better long-term health outcomes.
