Healthy Living

What Does a High Red Blood Cell (RBC) Count Mean?

Although having a high red blood cell count doesn’t always indicate a health problem, it could also be a symptom of a disease or disorder in certain cases.

What Does a High Red Blood Cell (RBC) Count Mean?


Red blood cells (RBCs), also called erythrocytes, are the cells that carry oxygen throughout the body. They are also one of the major components of blood. Having a high red blood cell (RBC) count means that the number of RBCs in the bloodstream is higher than normal. 

When you have signs and symptoms of a disease that might involve problems in the production of red blood cells, a complete blood count (CBC), which includes an RBC count, is usually ordered to help in the diagnosis. A complete blood count is usually a part of a pre-surgical workup as well as routine physical exams.

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Changes in the RBC count also mean that there are changes in the level of hemoglobin and hematocrit in the blood. When the RBC, hemoglobin, and hematocrit count are below the established normal range, the patient is said to be anemic. On the other hand, when a person has values that exceed the normal limit, he or she is said to be polycythemic. Too many RBCs can lead to a decreased flow of blood and other related health problems, while too few RBCs can significantly affect the amount of oxygen reaching the tissues. 

Healthcare providers may order a CBC when patients show some of the common signs and symptoms of anemia, such as:

Patients with a high RBC count may show any of the following signs and symptoms:

  • Dizziness
  • Headache
  • Visual disturbance
  • Flushing
  • Spleen enlargement

This blood test may also be regularly performed to help monitor patients with certain blood disorders, such as chronic anemia, bleeding problems, and polycythemia, including kidney disease.

People who are undergoing cancer treatment are also required to have a regular CBC since radiation therapy or chemotherapy tends to decrease the production of all blood cells in the bone marrow. 

Reference Range of RBC Count 

The following reference ranges are only a theoretical guideline and should not be used to interpret test results. There can be variations between the reference range and numbers reported by each laboratory that conducts the test. Please consult your healthcare provider for the interpretation of your test results.  


Conventional Units

SI Units

0-18 years old

Unavailable due to wide variability.

Refer to your child's laboratory report for the reference ranges.

Male (Adult)

4.5-5.9 x 106/μL

4.5-5.9 x 1012/L

Female (Adult)

4.5-5.1 x 106/μL

4.1-5.1 x 1012/L

What causes a high red blood cell (RBC) count?

Although having a high red blood cell count doesn’t always indicate a health problem, it could also be a symptom of a disease or disorder in certain cases. Lifestyle and health factors can also cause an increase in the red blood cell count. They include:

  • Living at higher altitudes
  • Cigarette smoking
  • The use of performance-enhancing drugs, such as protein injections, anabolic steroids, or erythropoietin (EPO)

The following are medical conditions that can cause high red blood cell (RBC) counts:

Polycythemia Vera (PV)

This rare blood disease develops when the body produces too many red blood cells (RBCs). When there is an overproduction of red blood cells, blood becomes abnormally thicker, making people more prone to developing blood clots. The formation of blood clots can affect the normal flow of blood through the veins and arteries, and cause a heart attack or stroke. 

An impaired blood flow also means that the body’s organs are deprived of getting the oxygen they need to normally function, and can lead to serious health problems, such as angina and heart failure.  

Polycythemia vera is a chronic blood disease that can be life-threatening if not properly diagnosed and treated. Although the condition has no cure, there are treatments that can help manage the disease and its complications. Treatment for PV may also involve more than one treatment method to help manage the disease. 

Low Oxygen Level

The body tries to compensate and increase the production of red blood cells for any medical condition that can cause low oxygen levels. These conditions include:

  • Chronic obstructive pulmonary disease (COPD)
  • Pulmonary fibrosis and other lung diseases
  • Heart disease (e.g., congenital heart disease)
  • Heart failure
  • Hemoglobinopathies (genetic disorders that reduce the RBC’s oxygen-carrying capacity, such as sickle-cell disease)
  • Nicotine or tobacco dependence
  • Sleep apnea

Renal or Kidney Disease

An abnormally functioning kidney due to renal disease, kidney transplant, and kidney cancer can cause the production of too much erythropoietin, which enhances the production of red blood cells. 

Certain Medications

Certain medications, such as methyldopa and gentamicin can increase red blood cell (RBC) counts. Methyldopa is a drug used for the treatment of hypertension (high blood pressure) and gentamicin is an antibacterial drug used for the treatment of bacterial infections in the blood. Make sure to inform your doctor about the medications you take. 


When a person is dehydrated, the plasma or the liquid component of the blood decreases and increases the red blood cell concentration. 

How is a high RBC count treated?

Your healthcare provider may recommend certain medications or procedures to help lower your RBC count, especially if a medical condition is causing the abnormal count.

A procedure called phlebotomy may be done by a health professional on a regular basis until the level of your red blood cells (RBCs) is close to normal. In this procedure, a needle is inserted into your vein to draw blood into a designated container or bag.

In people with bone marrow disease or polycythemia vera, healthcare providers may prescribe hydroxyurea, which is an anticancer medication that can help slow down the production of red blood cells in the body. Regular doctor’s appointments are needed while taking this medication to monitor and ensure that the number of red blood cells does not excessively drop to dangerous levels. 

When to See a Doctor

An elevated RBC count is usually discovered when doctors order blood tests to help diagnose a patient's condition. You can ask your doctor and discuss the results of your blood tests. Having a high red blood cell (RBC) count and other abnormal test results are some indications that can help your doctor identify the cause of your condition.  


Red Blood Cell Count (RBC). (July 2018)

Understanding Blood Counts. (n.d.)

High Red Blood Cell Count. (May 2018)

Polycythemia Vera. (n.d.)