Definition of RBC count:

An RBC count is a blood test that tells how many red blood cells (RBCs) you have.

RBCs contain hemoglobin, which carries oxygen. How much oxygen your body tissues get depends on how many RBCs you have and how well they work.

How the test is performed:

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

How to prepare for the test:

No special preparation is necessary for adults.

How the test will feel:

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed:

The RBC count is almost always part of the CBC (complete blood count) test.

The test can help diagnose anemia and other conditions affecting red blood cells.

Additional conditions under which an RBC count may be performed:

• Alport syndrome
• Drug-induced immune hemolytic anemia
• Hemolytic anemia due to G6PD deficiency
• Hereditary anemias, such as thalassemia
• Idiopathic autoimmune hemolytic anemia
• Immune hemolytic anemia
• Macroglobulinemia of Waldenstrom
• Paroxysmal nocturnal hemoglobinuria (PNH)
• Primary myelofibrosis