When you have a low blood count, this means your bone marrow is not making enough of one type of blood cells. Doctors call a low blood count cytopenia cytopenia: (sie-tuh-PEE-nee-uh) A shortage of one or more blood cell types. Also called a low blood count. . You can have one or more low blood counts.
Doctors use an important blood test called a complete blood count, or CBC for short, to measure the number of each blood cell in your blood sample. If the CBC shows a low number of red blood cells, white blood cells, or platelets, your doctor may look at the cells under a microscope. This is called a blood smear, and it can show if any blood cells are abnormal.
Low blood counts can have many causes, including vitamin deficiencies, bleeding, and rare bone marrow failure diseases like aplastic anemia, MDS and PNH. If your blood tests are abnormal, your doctor may do other blood tests or take a sample of your bone marrow bone marrow: The soft, spongy tissue inside most bones. Blood cells are formed in the bone marrow. to find out why.