by EBSCO Medical Review Board

A complete blood count (CBC) is a blood test that shows the number of blood cells. Anemia is diagnosed if RBC levels are too low. It may also suggest what type of anemia is present. Other tests or questions will help to confirm an anemia due to nutrition. Tests to rule out other causes include:

  • Blood smear—Blood is taken from your finger and smeared on a slide. RBCs can be looked at in a lab to look for problems in shape or size.
  • Reticulocyte count—Counts young RBCs to see how fast RBCs are being made. RBCs look different based on how old they are.
  • Serum iron, iron binding capacity, and ferritin—Tests to see if you have enough iron in your blood.
  • Folic acid and B12 levels—Needed to make healthy RBCs.
  • Hemoglobin electrophoresis—Looks for any issues that may be caused by problems with your genes.
  • RBC fragility—Looks for weak RBCs that have a higher chance of being destroyed.
  • Coombs tests—Finds antibodies that make RBCs more fragile.
  • Bone marrow biopsy—Bone marrow tissue is taken and looked at in a lab. RBCs are made in bone marrow.


Anemia. American Society of Hematology website. Available at: Accessed February 13, 2020.

Anemia in Adults-Approach to Patients. EBSCO DynaMed website. Available at: . Updated September 27, 2019. Accessed February 13, 2020.

Anemia in Older Adults. EBSCO DynaMed website. Available at: . Updated November 27, 2017. Accessed February 13, 2020.

Anemia. National Heart, Blood and Lung Institute website. Available at: Accessed February 13, 2020.

Complete blood count (CBC). Lab Tests Online—AACC website. Available at: Updated January 11, 2020. Accessed February 13, 2020.

Vieth JT, Lane DR. Anemia. Hematol Oncol Clin North Am. 2017 Dec;31(6):1045-1060.

Revision Information

  • Reviewer: EBSCO Medical Review Board Marcin Chwistek, MD
  • Review Date: 09/2019
  • Update Date: 10/30/2020