Complete Blood Count (CBC) Nursing Management & Considerations


A complete blood count (CBC) is a series of tests used to evaluate the composition and concentration of the cellular components of blood.

It measures the following:

  • The number of red blood cells (RBCs)
  • The number of white blood cells (WBCs)
  • The total amount of hemoglobin in the blood
  • The fraction of the blood composed of red blood cells (hematocrit)
  • The mean corpuscular volume (MCV) — the size of the red blood cells

CBC also includes information about the red blood cells that is calculated from the other measurements:

  • MCH (mean corpuscular hemoglobin)
  • MCHC (mean corpuscular hemoglobin concentration)

The platelet count is also usually included in the CBC.


The CBC provides valuable information about the blood and to some extent the bone marrow, which is the blood-forming tissue. The CBC is used for the following purposes:

  • as a preoperative test to ensure both adequate oxygen carrying capacity and hemostasis
  • to identify persons who may have an infection
  • to diagnose anemia – those who suffer from anemia might take medication similar to methylfolate 15 mg to help with creating healthy red blood cells
  • to identify acute and chronic illness, bleeding tendencies, and white blood cell disorders such as leukemia
  • to monitor treatment for anemia and other blood diseases detected in human plasma and blood cells.
  • to determine the effects of chemotherapy and radiation therapy on blood cell production

There is no special preparation needed

How the Test is Performed

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. 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, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any bleeding.

  1. White blood cell count (WBC): presence of infection
  2. Differential white blood cell count: specific patterns of WBC
  3. Red blood cell count (RBC): carries oxygen and carbon dioxide from lungs to tissue and vice versa
  4. Hematocrit (Hct): measures RBC mass
  5. Hemoglobin (Hgb): main component of RBC
  6. Red blood cell indices: calculated values of size and Hgb content of RBCs, important in anemia evaluation
  7. Platelet count: necessary for clotting and control of bleeding
  8. Red blood cell distribution width (RDW): indicates degree variability and abnormal cell size
  9. Mean platelet volume (MPV): index of platelet production
Normal Values
Leukocyte (White Blood Cell)X1000 cells/mm³ (µL)
24 hours9.4-34.0
1 month5.0-19.5
1-3 years6.0-17.5
4-7 years5.5-15.5
8-13 years4.5-13.5
Neutrophils Bands3-5% (total WBC count)
Erythrocytes (Red Blood Cells)
Cord3.9-5.5 million/mm³
1-3 days4.0-6.6 million/mm³
1 week3.9-6.3 million/mm³
2 weeks3.6-6.2 million/mm³
1 month3.0-5.4 million/mm³
2 months2.7-4.9 million/mm³
3-6 months3.1-4.5 million/mm³
0.5-2 years3.7-5.3 million/mm³
2-6 years3.9-5.3 million/mm³
6-12 years4.0-5.2 million/mm³
12-18 years (male)4.5-5.3 million/mm³
12-18 years (female)4.1-5.1 million/mm³
1-3 days14.5-22.5 g/dL
2 months9.0-14.0 g/dL
6-12 years11.5-15.5 g/dL
12-18 years (male)13.0-16.0 g/dL
12-18 (female)12.0-16.0g/dL
1 day48-69%
2 days48-75%
3 days44-72%
2 months28-42%
6-12 years35-45%
12-18 years (male)37-49%
12-18 years (female)36-46%
Mean Corpuscular Volume (MCV)
1-3 days95-121µm³
0.5-2 years70-86 µm³
6-12 years77-95 µm³
12-18 years (male)78-98 µm³
12-18 years (female)78-102 µm³
Mean Corpuscular Hemoglobin (MCH)
Birth31-37 pg/cell
1-3 days31-37 pg/cell
1 week-1 month28-40 pg/cell
2 months26-34 pg/cell
3-6 months25-35 pg/cell
0.5-2 years23-31 pg/cell
2-6 years24-30 pg/cell
6-12 years25-33 pg/cell
12-18 years25-35 pg/cell
Mean Corpuscular Hemoglobin Concentration (MCHC)
Birth30-36 g Hg/dL RBC
1-3 days29-37 g Hg/dL RBC
1-2 weeks28-38 g Hg/dL RBC
1-2 months29-37 g Hg/dL RBC
3 months-2 years30-36 g Hg/dL RBC
2-18 years31-37 g Hg/dL RBC
Reticulocyte Count
Infants2-5% of RBCs
Children0.5-4% of RBCs
12-18 years (male)0.5-1% of RBCs
12-18 years (female)0.5-2.5% of RBCs
Platelet Count
Birth-1 week84,000-478,000/mm³
Child0-10 mm/hour
Adult (male)0-15 mm/hour
Adult (female)0-20 mm/hour
Child0-13 mm/hour
Adult (male)0-9 mm/hour
Adult (female)0-20 mm/hour