A CBC requires a small blood specimen. Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand.
Preparation: The skin should be cleaned with alcohol or iodine before the test. The patient should be seated comfortably or reclining.
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. After the blood is drawn, there may be some throbbing.
Although the CBC test is very safe, any blood drawing has a slight risk of complication, including:
- Oozing of blood from puncture site
- Fainting or feeling lightheaded
- Hematoma (blood accumulating under the skin)
- Multiple punctures to locate veins
- Infection (a slight risk any time the skin is broken)
Review Date 3/19/2012
Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.