Answer: A complete blood count (CBC) test measures how much hemoglobin is in your blood and counts the number of white blood cells and blood platelets. If your hemoglobin is low, you are anemic. In patients with kidney disease, anemia is often caused by low erythropoietin (EPO) levels. EPO is a hormone normally made by the kidneys and helps the bone marrow make red blood cells. If the CBC shows you are anemic, your doctor prescribes EPO, a synthetic form of the hormone, or increases your dose if you are already taking the medication.

A CBC also measures the number and kinds of white blood cells. A low white blood cell count can be caused by medications used to treat chronic kidney disease (CKD) and by immunosuppressive drugs that prevent transplant rejection. A low white blood cell count may require a change in the doses of these medicines. A high white blood cell count can mean that you have an infection.

When people are cut, blood platelets help blood to clot. A very low platelet count can be caused by some kinds of kidney diseases and may indicate that there is a danger of bleeding.

To help adjust a patient’s EPO dose, we measure hemoglobin of hemodialysis patients monthly. Periodically, we do a CBC in patients not yet on dialysis, depending on whether they are on EPO and when we last had to change the dose. Kidney transplant patients also have periodic CBCs depending on how long ago they had their transplant and whether or not we have change their doses of anti-rejection medications.

Answer provided by George Aronoff, MD, FACP. Dr. Aronoff is Professor of Medicine and Pharmacology and Chief, Division of Nephrology at the University of Louisville School of Medicine, Louisville, Ky. He is also a member of the AAKP Medical Advisory Board.

The American Association of Kidney Patients presents Ask the Doctor, an opportunity for readers to submit kidney related health questions to healthcare professionals who specialize in an area of concern. The answers are not to be construed as a diagnosis and therefore, alterations in current healthcare should not occur until the patient’s physician is consulted.

This article originally appeared in the June/July 2005 issue of Kidney Beginnings: The Magazine, Vol. 4, No. 2.