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A red blood cell count is a blood test that your doctor uses to find out how many red blood cells (RBCs) you have in your blood. 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.
According to the American Association for Clinic Chemistry (AACC), the test is almost always a part of a complete blood cell (CBC) test. A CBC test measures the number of all types of components in the blood, including:
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 signs of low blood oxygen include:
A CBC test will often be part of a routine physical exam because it’s a good 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.
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:
There’s 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.
Talk to your doctor to find out if any other preparation is necessary.
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.
According to the Mayo Clinic:
However, these ranges may vary slightly depending on the laboratory or doctor.
You have erythrocytosis if your RBC count is higher than normal. This may be due to:
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. Be sure to tell your doctor about any medications you take.
If the number of RBCs is lower than normal it may be caused by:
Certain drugs can also lower your RBC count, especially:
Your doctor will discuss any abnormal results with you. A high or low RBC count may help identify the cause of your symptoms. Depending on your results and your situation, your doctor may need to order additional tests or treatments.
Written by: Jacquelyn Cafasso and Ana Gotter
Published on: Oct 14, 2015
Medically reviewed on: Apr 06, 2017: Deborah Weatherspoon, PhD, RN, CRNA
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