High Red Blood Cell Count
A high red blood cell count means the body has more red blood cells than normal in the bloodstream. Medical conditions like heart or lung disease, dehydration, or certain medications can cause this.
Sometimes, the body makes extra cells to carry more oxygen, or the blood becomes more concentrated. Factors like living at high altitudes, smoking, or kidney issues can also play a role. Lifestyle habits and environmental changes can influence red blood cell levels.
Definition of Symptom
A high red blood cell count means the number of red blood cells in the blood is above the normal range. Doctors often check this as part of a complete blood count (CBC), which also looks at hemoglobin and hematocrit.
In this condition, the blood contains more RBCs than expected for a person’s age and sex. This can happen because the body makes extra cells or because there is less plasma, making the RBC count appear higher.
Key Terms
| Term | Meaning |
|---|---|
| RBC Count | Number of red blood cells per volume of blood. |
| Hemoglobin | Protein in RBCs that carries oxygen. |
| Hematocrit | Percentage of blood made up of RBCs. |
| Erythrocytes | Another name for red blood cells. |
A high count is sometimes called erythrocytosis or polycythemia. It can be a primary condition, such as polycythemia vera, or secondary to other issues like chronic lung disease. Common symptoms may include:
- Headaches
- Dizziness
- Fatigue
- Blurred vision
- Itchy skin, especially after a warm shower
Not everyone with an elevated red blood cell count will notice symptoms. Sometimes, routine blood tests reveal the finding. When symptoms occur, they often relate to thicker blood and slower blood flow.
Possible Causes/ Diseases Condition
A high red blood cell count, also called erythrocytosis or polycythemia, can happen for different reasons. Some causes relate to bone marrow disorders, while others develop as a response to low oxygen or other health problems.
Primary polycythemia, such as polycythemia vera, happens when the bone marrow makes too many red blood cells without a clear trigger. This often links to genetic changes and can make blood thicker. Primary familial and congenital polycythemia is a rare inherited form.
Secondary polycythemia happens when another condition causes extra red blood cell production. Chronic lung disease like COPD, emphysema, or pulmonary hypertension can cause this. Low oxygen from sleep apnea, hypoventilation syndrome, or living at high altitude can also trigger it.
Certain heart diseases, such as congestive heart failure, may reduce oxygen delivery and cause the body to make more red blood cells. Tumors that release too much erythropoietin—such as renal cell carcinoma, hepatocellular carcinoma, or adrenal adenoma—can have the same effect.
Blood cancers like leukemia or myelofibrosis may also raise counts. Sometimes, stress polycythemia or relative polycythemia happens when plasma volume drops, often from dehydration, making the red blood cell concentration seem higher.
Examples of Related Conditions
| Condition Type | Examples |
|---|---|
| Primary | Polycythemia vera, Primary familial and congenital polycythemia |
| Secondary | COPD, Sleep apnea, Heart disease, Kidney cancer, Liver cancer |
| Relative | Stress polycythemia, Dehydration |
Some cases link to risk factors like smoking, chronic lung problems, or certain genetic traits.
Other Non-Disease Causes
A high red blood cell count can happen for reasons unrelated to illness. Sometimes, the body responds to environmental or lifestyle factors that increase the need for oxygen.
- Dehydration is one common cause. When the body loses fluids, the blood becomes more concentrated, which can make the red blood cell count appear higher than normal.
- Living at high altitude can also raise red blood cell levels. The thinner air contains less oxygen, so the body makes more red blood cells to carry enough oxygen to tissues.
- Smoking and carbon monoxide exposure reduce the blood’s ability to carry oxygen. In response, the body may create more red blood cells. Quitting smoking or avoiding polluted environments can help lower this effect over time.
- The use of anabolic steroids can increase red blood cell production. These substances may be prescribed for certain medical purposes but are also used by some athletes, which can lead to elevated counts.
- Regular exercise, especially endurance training, can slightly increase red blood cell numbers as the body adapts to higher oxygen needs. This change is usually mild and part of a normal response.
| Factor | Effect on RBC Count |
|---|---|
| Dehydration | Concentrates blood |
| High altitude | Increases production |
| Smoking | Reduces oxygen delivery |
| Carbon monoxide | Lowers oxygen binding |
| Anabolic steroids | Stimulates production |
How It Causes the Symptom
A high red blood cell count often starts with increased red blood cell production in the bone marrow. Higher levels of erythropoietin, a hormone that controls red blood cell production, can trigger this. When blood oxygen levels drop, the body releases more erythropoietin. Low oxygen, or hypoxia, can happen in lung disease, heart disease, or living at high altitude.
Some cases link to a JAK2 gene mutation. This genetic change can make the bone marrow produce too many red blood cells even when oxygen levels are normal, as seen in polycythemia vera. Extra red blood cells make the blood thicker. This can slow circulation and reduce oxygen delivery to some tissues, even if the blood carries more total oxygen. Possible pathways leading to high counts:
| Cause | Effect on RBC Production | Example Conditions |
|---|---|---|
| Low blood oxygen | Increases erythropoietin | COPD, sleep apnea |
| JAK2 mutation | Direct bone marrow stimulation | Polycythemia vera |
| High altitude | Stimulates red blood cell production | Mountain living |
| Kidney changes | Too much erythropoietin | Kidney tumors |
In each pathway, the problem either increases the need for oxygen transport or directly stimulates the bone marrow. The result is a measurable rise in red blood cell count on a blood test.
Possible Complications
A high red blood cell count can make the blood thicker. Thicker blood can slow circulation and raise the risk of blood clots. Clots may form in veins or arteries and can block blood flow to vital organs. Serious events can include a clot traveling to the lungs (pulmonary embolism), or a stroke or heart attack if a clot blocks blood supply to the brain or heart.
The heart may need to work harder to pump thicker blood. Over time, this strain can contribute to heart failure, especially in people with other heart conditions. An enlarged spleen can develop if the spleen works harder to filter extra blood cells. This may cause discomfort or pain in the upper left abdomen.
Some people may also have higher white blood cell or platelet counts along with high red blood cell levels. These changes can further increase clotting risks. In some cases, doctors may lower red blood cell levels by removing blood from the body, similar to donating blood, to reduce thickness and improve flow.
| Complication | Possible Effect |
|---|---|
| Thrombosis | Blocked blood flow |
| Pulmonary embolism | Reduced oxygen in blood |
| Heart failure | Weakened heart function |
| Splenomegaly | Abdominal discomfort |
| Leukocytosis | Higher infection risk |
| Thrombocytosis | Increased clotting risk |
When to Seek Medical Attention
Contact a healthcare provider if you notice persistent or worsening symptoms linked to a high red blood cell count. These symptoms may signal an underlying health problem that needs prompt evaluation. Common signs that require attention include:
| Symptom | Why It Matters |
|---|---|
| Headache | Thicker blood can reduce oxygen flow and cause headaches. |
| Dizziness | Reduced blood flow to the brain can cause dizziness. |
| Shortness of Breath | Low oxygen levels or circulation issues may cause shortness of breath. |
| Fatigue or Weakness | The heart may work harder to pump thickened blood, causing fatigue or weakness. |
| Nosebleeds | Blood vessels under more pressure can lead to nosebleeds. |
| Joint Pain | Reduced circulation may cause joint pain. |
| Vomiting or Diarrhea | Dehydration from vomiting or diarrhea may worsen blood thickness. |
If you suddenly experience severe headache, sudden dizziness, or shortness of breath, seek urgent medical care. These symptoms could point to complications like blood clots or low oxygen delivery. Consult a doctor if mild symptoms, such as fatigue or weakness, last for more than a few days without improvement. Even minor signs can indicate a developing problem.
