A complete blood count is also called a CBC for short. It is a screening test that is used to diagnose many different disorders of the blood, including anemia and infection. A CBC measures the following important features of the blood:
- number of red blood cells, called RBCs for short
- number of white blood cells, called WBCs for short
- number of platelets
- total amount of hemoglobin in the blood
- percentage of blood composed of cells, called hematocrit
- other special tests as needed
The test is fast and virtually pain free.
How Is This Test Done?
To take a blood sample from a vein on your forearm or hand, your doctor or nurse will follow these steps.
- Clean the skin over your vein with an antiseptic.
- Wrap a strong rubber tube, called a tourniquet, around your upper arm. Doing this enlarges the veins in your lower arm by restricting blood flow through them. Enlarged veins are easier to take blood from.
- Gently insert a small needle into your vein.
- Collect a small sample of your blood in a syringe or vial.
- Remove the tourniquet.
- Withdraw the needle.
- Cover the puncture site with a bandage and apply pressure to stop any bleeding.