What a Complete Blood Count Can Tell You About Lupus

A CBC looks at your red and white blood cells and can help diagnose lupus

blood sample vials on medical record
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Your physician has several diagnostic tools they can use to determine whether or not you have lupus. If your doctor suspects you have lupus, they will conduct a complete medical history, physical examination, skin and kidney biopsies, and various lab tests.

Typical lab tests your doctor might order include:

  • Other autoantibody tests (anti-dsDNA, anti-Sm, anti-RNP, anti-Ro [SSA], anti-La [SSB])
  • Anticardiolipin antibody test

While all of these are important for helping diagnose lupus, typically the first test a physician will request is the complete blood count (CBC).

What Is a CBC?

A CBC consists of a number of different blood tests and is commonly used as a broad screening tool. The tests that make up a CBC include: 

  • White blood cell count (WBC): White blood cells aid the body in fighting infections, and can be indicators of infection, as well. This test measures the number of white blood cells in the blood. Too many white blood cells or too few can both be significant indicators.
  • White blood cell differential: Counts the various types of WBCs.
  • Red blood cell count (RBC): The number of red blood cells present. Red blood cells contain hemoglobin and function as oxygen carriers. As with white blood cells, both increases and decreases in number can matter.
  • Red cell distribution width: Measures the variation in the size of red blood cells.
  • Hemoglobin: Hemoglobin is the protein in red blood cells that carries oxygen. This measures how much of that oxygen-carrying protein is in the blood.
  • Mean corpuscular hemoglobin: Tells how much hemoglobin is inside a red blood cell.
  • Mean corpuscular hemoglobin concentration: Measures the average concentration of hemoglobin inside a red blood cell.
  • Hematocrit: The percentage of red blood cells in whole blood.
  • Platelet count: The number of platelets in the blood. Platelets are a type of blood cell that prevents bleeding by forming clots.
  • Mean platelet volume: Measures the size of platelets and can give information about platelet production in bone marrow.

Results might tell a doctor that you have issues with fluid volume like dehydration or blood loss. Your CBC results can also help diagnose infection, allergies, and problems with blood clotting. Other results may indicate various types of anemia.

What Your CBC Can Tell Your Doctor About Lupus

If your doctor suspects you have lupus, they will focus on your RBC and WBC counts. Low RBC counts are frequently seen in autoimmune diseases like lupus. However, low RBC counts can also indicate blood loss, bone marrow failure, kidney disease, hemolysis (RBC destruction), leukemia, malnutrition, and more.

Low WBC counts can point toward lupus as well as bone marrow failure and liver and spleen disease.

If your CBC comes back with high numbers of RBCs or a high hematocrit, it could indicate a number of other issues including lung disease, blood cancers, dehydration, kidney disease, congenital heart disease, and other heart problems.

Low RBCs indicate an ​autoimmune disease.

High WBCs, called leukocytosis, may indicate an infectious disease, inflammatory disease, leukemia, stress, and more. 

While this information can help you decipher your lab work, always talk to your doctor if your receive abnormal blood test results. A blood test is just a piece of the puzzle when it comes to making a diagnosis. 


CBC. Lab Tests Online. February 2009.

Handout on Health: Systemic Lupus Erythematosus The National Institute of Arthritis and Musculoskeletal and Skin Diseases. August 2003.

CBC Medline Plus Medical Encyclopedia. January 2009.