Your RBC count may become too high or too low if you have certain health conditions, including nutritional deficiencies, erythrocytosis, and some chronic health conditions.

A red blood cell count is a blood test that your doctor uses to find out how many red blood cells (RBCs) you have. It’s also known as an erythrocyte count.

The test is important because RBCs contain hemoglobin, which carries oxygen to your body’s tissues. The number of RBCs you have can affect how much oxygen your tissues receive. Your tissues need oxygen to function.

If your RBC count is too high or too low, you could experience symptoms and complications.

If you have a low RBC count, symptoms could include:

If you have a high RBC count, you could experience symptoms such as:

  • fatigue
  • shortness of breath
  • joint pain
  • tenderness in your palms or soles of your feet
  • itching skin, particularly after a shower or bath
  • sleep disturbance

If you experience these symptoms your doctor can order an RBC count.

According to the Association for Clinical Biochemistry and Laboratory Medicine, the test is almost always part of a complete blood count (CBC). A CBC measures all components in the blood, including:

  • red blood cells
  • white blood cells
  • hemoglobin
  • hematocrit
  • platelets

Your hematocrit is the volume of red blood cells in your body. A hematocrit test measures the ratio of RBCs in your blood.

Platelets are small cells that circulate in the blood and form blood clots that allow wounds to heal and prevent excessive bleeding.

Your doctor may order the test if they suspect you have a condition that affects your RBCs, or if you show symptoms of low blood oxygen. These could include:

A CBC will often be part of a routine physical exam. It can be an indicator of your overall health. It may also be performed before a surgery.

If you have a diagnosed blood condition that may affect RBC count, or you’re taking any medications that affect your RBCs, your doctor may order the test to monitor your condition or treatment. Doctors can use CBCs to monitor conditions like leukemia and infections of the blood.

An RBC count is a simple blood test performed at your doctor’s office. A healthcare professional will draw blood from your vein, usually on the inside of your elbow. They will then:

  1. clean the puncture site with an antiseptic
  2. wrap an elastic band around your upper arm to make your vein swell with blood
  3. gently insert a needle into your vein and collect the blood in an attached vial or tube
  4. remove the needle and elastic band from your arm

After collecting your blood sample, your doctor’s office will send it to a laboratory for analysis.

There’s typically no special preparation needed for this test. But you should tell your doctor if you’re taking medications. These include any over-the-counter (OTC) drugs or supplements.

Your doctor will be able to tell you about any other necessary precautions.

As with any blood test, there’s a risk of bleeding, bruising, or infection at the puncture site. You may feel moderate pain or a sharp pricking sensation when the needle enters your arm.

RBC ranges are measured in terms of cells per microliter (µL). Normal ranges for RBC differ based on age and sex assigned at birth.

Normal RBC range (million cells/µL)
Adult, assigned female at birth4.2 – 5.4
Adult, assigned male at birth4.7 – 6.1
Child, 1 – 18 years4.0 – 5.5
Infant, 6 – 12 months3.5 – 5.2
Infant, 2 – 6 months3.5 – 5.5
Infant, 2 – 8 weeks4.0 – 6.0
Newborn4.8 – 7.1

These ranges may vary depending on the laboratory or doctor. Ranges may also differ for those who are pregnant.

If your number of RBCs is lower than normal, you have anemia. This can be caused by a decrease in RBC production or by the destruction or loss of RBCs. There are many possible causes for anemia.

Nutritional Deficiency

Iron-deficiency anemia is the most common type of anemia, but lack of other nutrients can also cause your RBC count to decrease. These include:

Bone marrow failure

In rare cases, your bone marrow might stop making new blood cells. This is called aplastic anemia.

Aplastic anemia might be an autoimmune disorder. Certain drugs, viruses, toxins, or radiation may also cause aplastic anemia.


Hemolysis is the destruction of red blood cells. Common causes of hemolysis include:

  • autoimmune reaction to blood transfusion
  • infection
  • inherited conditions, like sickle cell anemia

Chronic conditions

Underlying health conditions that cause inflammation may affect the way your body processes erythropoietin (EPO). EPO is a hormone that causes bone marrow to produce RBCs.

EPO is produced in the kidneys. If you have chronic kidney disease, you might produce less EPO than normal.

Other chronic conditions that may cause a low RBC count include, but are not limited to:

Other conditions

Other possible reasons for a lower than normal RBC count include:


Certain drugs can also lower your RBC count, especially:

  • chemotherapy drugs
  • chloramphenicol, which treat bacterial infections
  • quinidine, which can treat irregular heartbeats
  • hydantoins, traditionally used to treat epilepsy and muscle spasms

If your RBC count is higher than normal, you have erythrocytosis. This causes your blood to be thicker than normal and can increase your risk of blood clots.

Primary erythrocytosis

Primary erythrocytosis is when your own body causes you to produce more RBCs. This is usually due to a problem with cells in your bone marrow. The condition is often inherited.

One such condition is polycythemia vera, a bone marrow disease that causes overproduction of RBCs and is associated with a genetic mutation.

Secondary erythrocytosis

Secondary erythrocytosis is when an external factor increases your RBC count. This could be due to a disease, drug, or another cause.

Some medical conditions that can cause a high red blood cell count include:

Certain drugs can increase your RBC count, including:

  • gentamicin, an antibiotic used to treat bacterial infections in the blood
  • methyldopa, often used to treat high blood pressure
  • performance-enhancing drugs, like anabolic steroids or protein injections
  • diuretics

Tell your doctor about any medications you take.

Other potential reasons for an elevated RBC count include:

Blood cancers can affect the production and function of red blood cells. They can also result in unusual RBC levels.

Each type of blood cancer has a unique impact on RBC count. The three main types of blood cancer are:

  • leukemia, which impairs the bone marrow’s ability to produce platelets and red blood cells
  • lymphoma, which affects the white cells of the immune system
  • myeloma, which prevents normal production of antibodies

Your doctor will discuss any abnormal results with you. Depending on the results, they may need to order additional tests.

These can include blood smears, where a film of your blood is examined under a microscope. Blood smears can help detect abnormalities in the blood cells (such as sickle cell anemia), white blood cell disorders such as leukemia, and bloodborne parasites like malaria.

A bone marrow biopsy can show how the different cells of your blood are made within your bone marrow. Diagnostic tests, such as ultrasounds or electrocardiograms, can look for conditions affecting the kidneys or heart.

Treatment for a low RBC count

All types of anemia require treatment. Your treatment will depend on what’s causing your anemia.

  • Iron deficiency. You can take iron supplements or receive iron infusions through your veins.
  • Vitamin deficiency. You can take vitamin supplements.
  • Bone marrow failure. Your doctor may prescribe certain medications. If medications don’t help, you may need a bone marrow transplant.
  • Chronic conditions. Your doctor will usually focus on treating the underlying condition. Sometimes, they may prescribe an EPO-stimulating agent.
  • Blood loss. A blood transfusion can bring in more RBCs to your body.

Treatment for a high RBC count

If you have erythrocytosis, you may need a regular phlebotomy. This removes a small amount of blood from your body in order to lower your RBC count.

If phlebotomies don’t work, your doctor may prescribe hydroxyurea (Hydrea or Droxia) to reduce your RBC count.

You may also need aspirin to help with potential blood clots.

Lifestyle changes can affect your RBC count. Some changes that can help increase your RBC count include:

  • maintaining a healthy diet and avoiding vitamin deficiencies
  • exercising regularly, which requires the body to use up more oxygen
  • avoiding aspirin
  • reducing alcohol consumption

If you need to decrease your RBC count, the following lifestyle changes may help:

  • reducing the amount of iron and red meat that you consume
  • drinking more water
  • avoiding diuretics, such as drinks containing caffeine or alcohol
  • quitting smoking

Dietary changes

Dietary changes can play a major part in home treatment by managing your RBC count.

You may be able to increase your RBC with the following dietary changes:

  • adding iron-rich foods (such as meat, fish, poultry, tofu), as well as dried beans, peas, and leafy green vegetables (such as spinach) to your diet
  • increasing copper in your diet with foods like shellfish, poultry, and nuts
  • getting more vitamin B12 with foods like eggs, meats, and fortified cereals

An RBC count that is either too high or too low can have serious health complications.

There is much you can do on your own to manage your RBC count, staring with a balanced diet and regular exercise. If you have blood cancers or chronic conditions that can affect RBC count, these lifestyle and dietary habits may be especially important.

Consult a doctor if you experience fatigue or shortness of breath. These are often symptoms of an abnormal RBC count.