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Red Blood Cell Count (RBC)

What is a red blood cell count?

Key points

  1. The red blood cell count is an important test because the number of red blood cells (RBCs) you have can affect how much oxygen your tissues receive.
  2. Fatigue and shortness of breath can be symptoms of either a low RBC count or a high RBC count.
  3. Certain medical conditions, dietary habits, and medications can all affect your RBC count.

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 effectively.

Symptoms of an abnormal count

If your red blood cell count is either too high or too low, you could experience accompanying symptoms and complications.

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

  • fatigue
  • shortness of breath
  • feeling dizzy, weak, or lightheaded, particularly when you change positions quickly
  • increased heart rate
  • headaches
  • pale skin

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

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

If you experience symptoms of either a low or high RBC count, your doctor can order a simple RBC count.

Why do I need a red blood cell count?

According to the American Association for Clinical Chemistry (AACC), the test is almost always a part of a complete blood count (CBC) test. A CBC test measures the number of all types of 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, and a hematocrit test measures the ratio of RBCs in your blood.

Platelets are small cells that circulate within the blood and form blood clots when needed, which allows wounds to heal and can prevent excessive bleeding.

Your doctor may perform the test if they suspect you have a condition that affects your RBCs or if there’s any sign that you have low blood oxygen. The symptoms of low blood oxygen include:

  • bluish discoloration of the skin
  • confusion
  • irritability and restlessness
  • irregular breathing

A CBC test will often be part of a routine physical exam because 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 CBC tests to monitor conditions such as leukemia and infections of the blood.

Read more: CBC (complete blood count) »

How is the test performed?

An RBC count is a simple blood test performed by a healthcare provider at your doctor’s office. They will draw blood from your vein, usually on the inside of your elbow. The steps involved in the blood draw typically are:

  • The healthcare provider will clean the puncture site with an antiseptic.
  • They will wrap an elastic band around your upper arm to make your vein swell with blood.
  • They will gently insert a needle into your vein and collect the blood in an attached vial or tube.
  • They will then remove the needle and elastic band from your arm.
  • The healthcare provider will send your blood sample to a laboratory for analysis.

How should I prepare for the test?

There’s typically no special preparation required for this test. However, you should tell your doctor if you’re taking medications, including any over-the-counter drugs or supplements.

Your doctor will also be able to tell you if any other precautions are necessary.

What are the risks of taking the test?

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 first enters your arm.

What do the results mean?

According to the Leukemia & Lymphoma Society,

  • The normal RBC range for men is 4.7 to 6.1 million cells per microliter.
  • The normal RBC range for women who aren’t pregnant is 4.2 to 5.4 million cells per microliter.
  • The normal RBC range for children is 4.0 to 5.5 million cells per microliter.

However, these ranges may vary slightly depending on the laboratory or doctor.

Higher than normal

You have erythrocytosis if your RBC count is higher than normal. This may be due to:

  • cigarette smoking
  • congenital heart disease
  • dehydration
  • renal cell carcinoma, which is a type of kidney cancer
  • pulmonary fibrosis
  • polycythemia vera, a bone marrow disease that causes overproduction of RBCs and is associated with a genetic mutation

When you move to a higher altitude, your RBC count may increase for several weeks because there’s less oxygen present in the air.

Certain drugs, such as gentamicin and methyldopa, can also increase your RBC count. Gentamicin is an antibiotic used to treat bacterial infections in the blood. Methyldopa is often used to treat high blood pressure and works by relaxing the blood vessels to allow blood to flow more easily through the body. Be sure to tell your doctor about any medications you take.

A high RBC count may be a result of sleep apnea, pulmonary fibrosis, and other conditions that cause low oxygen levels in the blood. Performance-enhancing drugs such as protein injections and anabolic steroids can also increase RBCs. Kidney disease and kidney cancers can lead to high RBC counts as well.

Lower than normal

If the number of RBCs is lower than normal, it may be caused by:

Anemia is a condition where there are not enough healthy red blood cells to adequately carry oxygen throughout the body. There are many forms and causes of anemia, including:
  • iron deficiency anemia, which is often easily treated
  • sickle cell anemia, which results in red blood cells having an abnormal crescent shape and dying quickly
  • vitamin deficiency anemia, which often stems from low levels of vitamin B-12
Regardless of the cause of anemia, it needs to be treated. People with anemia typically feel tired and weak. They may also experience headaches, cold hands and feet, dizziness, and irregular heartbeats.
  • anemia
  • bone marrow failure
  • erythropoietin deficiency, which is the primary cause of anemia in patients with chronic kidney disease
  • hemolysis, or RBC destruction caused by transfusions and blood vessel injury
  • internal or external bleeding
  • leukemia
  • malnutrition
  • multiple myeloma, which is a cancer of the plasma cells in bone marrow
  • nutritional deficiencies, including deficiencies in iron, copper, folate, and vitamins B-6 and B-12
  • pregnancy
  • thyroid disorders

Certain drugs can also lower your RBC count, especially:

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

Red blood cells and blood cancers

Blood cancers can affect both 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

What if I have abnormal results?

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

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 may be done to take a closer look at how the different cells of your blood are being made within your bone marrow. Diagnostic tests, such as ultrasounds or electrocardiograms, can look for conditions affecting the kidneys or heart.

Lifestyle changes can directly affect your RBC count. Some of these changes include:

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

Specific dietary changes can play a major part in home treatment of increasing or lowering your red blood count.

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

  • adding iron-rich foods such as spinach to your diet
  • increasing copper in your diet with foods like shellfish, poultry, and nuts
  • getting more vitamin B-12 with foods like eggs, meats, and fortified cereals

You may be able to decrease your RBC with the following lifestyle changes:

  • 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

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