Erythrocytosis is having a high concentration of red blood cells. Your levels may be high for many reasons. Some causes, like dehydration, are less concerning than others, like polycythemia vera, a serious blood disorder. Getting diagnosed and receiving treatment can prevent complications associated with erythrocytosis, like life-threatening blood clots.
Erythrocytosis involves having a higher-than-normal concentration of red blood cells (erythrocytes) in your blood. Your blood consists of solid parts, including red blood cells, white blood cells and platelets. It also includes a liquid portion called plasma. Erythrocytosis describes having too many red blood cells (a solid part) in relation to plasma (the liquid part).
Erythrocytosis is also commonly called polycythemia.
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Red blood cells are important because they transport oxygen throughout your body. They keep your tissues oxygenated, nourished and healthy.
Too many red blood cells can impact your body in a variety of ways depending on what’s causing your erythrocytosis. Some effects are mild while others are more serious. Many people only experience unpleasant symptoms, like headache or fatigue. More serious causes of erythrocytosis can cause your blood to become too thick, putting you at risk of blood clots, heart attacks or strokes.
It’s important to work with your provider to determine what’s causing your erythrocytosis so you receive the right treatment to provide symptom relief or prevent complications, as needed.
Erythrocytosis is classified based on the blood composition that causes the high concentration of red blood cells.
Absolute erythrocytosis involves a greater variety of causes than relative erythrocytosis. It’s further broken down based on whether its causes are considered primary or secondary.
Primary erythrocytosis results from problems in the spongy tissue inside of your bones called bone marrow. Bone marrow is the “primary” site in your body where red blood cells get made.
With primary erythrocytosis, red blood cell production increases in your bone marrow because of a genetic defect in the cells that eventually mature into red blood cells. These cells are called stem cells or progenitor cells. A genetic defect is an error in a cell’s code that tells it how to behave. A genetic defect can cause a cell to multiply out of control, creating too many red blood cells.
You can develop a genetic mutation over time (acquired), or you may be born with a genetic disorder (inherited).
Secondary erythrocytosis results from problems outside of your bone marrow. Most secondary erythrocytosis involves your body producing too much of a hormone called erythropoietin (EPO). Like all hormones, EPO is a chemical messenger. EPO tells your bone marrow to make more red blood cells.
For example, conditions that deprive your body of oxygen, like lung disease, trigger your body to produce more EPO. EPO tells your bone marrow to produce more red blood cells. Red blood cells, in turn, transport more oxygen to your body’s tissues. With secondary erythrocytosis, the red blood cell production is too much.
Some genetic conditions can also cause secondary erythrocytosis. Unlike primary erythrocytosis, these mutations don’t involve genetic mutations in your bone marrow.
Many factors can influence what’s considered a normal concentration for red blood cells. Your age, sex and even the altitude where you live all play a role.
Erythrocytosis is associated with elevated hematocrit and/or hemoglobin levels in adults. Your provider can measure these levels during a blood test.
Not having enough fluids can cause relative erythrocytosis. Vomiting, diarrhea and medicine called diuretics can cause you to have too little liquid in your blood. A diuretic helps your kidneys move water out of your body. You may need diuretics if you have high blood pressure or if excess fluid has collected in your body.
Primary and secondary erythrocytosis have different causes.
Primary erythrocytosis often results from a genetic mutation that affects your bone marrow. Causes include:
Secondary erythrocytosis usually involves high levels of EPO. Causes include:
Your symptoms (including how severe they are) will depend on what’s causing your erythrocytosis. For example, secondary causes of erythrocytosis may cause symptoms that include:
Primary causes of erythrocytosis may cause more severe symptoms, including:
Your healthcare provider may perform various tests and procedures to determine what’s causing your high concentration of red blood cells. To start, they’ll rule out relative erythrocytosis (too little plasma in your blood) by asking questions about your medical history, medicines you’re taking, lifestyle and symptoms. They may also perform a physical exam.
The next step is to determine whether your erythrocytosis is primary or secondary. In addition to considering the information above, your provider may perform several tests.
Your provider may perform any of the following tests to diagnose erythrocytosis.
Your provider may perform other tests, including imaging and a bone marrow biopsy if they suspect a specific condition like polycythemia vera.
Most causes of erythrocytosis can’t be cured. Instead, treatment can help ease symptoms. With more serious causes of erythrocytosis, your provider may provide treatments to prevent potential complications, like blood clots.
Phlebotomy is the most common treatment for polycythemia vera. Your healthcare provider will remove blood to eliminate excess red blood cells and reduce your overall blood volume. Secondary causes of erythrocytosis don’t often require this treatment.
Your provider may recommend you take a low dosage of aspirin regularly if you’re at high risk of developing blood clots. Your provider may also prescribe medicines that can lower your red blood cell count, including:
Your provider may recommend specific medications and procedures to treat the underlying condition causing erythrocytosis.
Your experience depends on what’s causing your erythrocytosis. Many inherited causes of primary erythrocytosis only cause mild symptoms and aren’t life-threatening. More serious conditions, like polycythemia vera, require lifelong treatment.
Follow your provider’s instructions based on your condition’s causes and severity. In the meantime, specific lifestyle changes that can help include:
It’s a good idea to know the signs of a blood clot if you have a condition related to your erythrocytosis that puts you at risk. Get immediate medical attention if you notice signs of the following conditions:
A note from Cleveland Clinic
Erythrocytosis involves having a higher-than-normal concentration of red blood cells (erythrocytes) in your blood. Your healthcare provider will work with you to determine what’s causing your high concentration of red blood cells. In some instances, simple lifestyle changes — like reducing or stopping a medication — may fix the issue. If a more serious condition is causing your erythrocytosis, your provider will monitor your condition closely to ensure you receive the treatment you need.
Last reviewed by a Cleveland Clinic medical professional on 07/05/2022.
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