What Are Low Blood Counts?

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. 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 to find out why.

What are the symptoms of low blood counts?

The symptoms of bone marrow failure diseases like aplastic anemia, MDS and PNH are caused by low blood counts. The specific symptoms depend on which type of blood cell is affected. Read the section below to see the symptoms for each type of cell.

You may have many of these symptoms or just one or two of them. And you may get a new symptom at any point in the course of your illness.

Low Red Blood Cell Count

A low red blood cell count is called anemia. If you have a low red blood cell count, you may:

  • Feel a little tired or very tired.
  • Feel less alert or have trouble concentrating.
  • Have a loss of appetite or lose weight.
  • Have paler-than-normal skin.
  • Have trouble breathing.
  • Have rapid heartbeat.
  • Have reduced ability to exercise or climb stairs.

Low White Blood Cell Count

A low white blood cell count is called neutropenia. If you have a low white blood cell count, you may:

  • Have repeated fevers and infections.
  • Get bladder infections that may make it painful to pass urine, or make you urinate more often.
  • Get lung infections that cause coughing and difficulty breathing.
  • Get mouth sores.
  • Get sinus infections and a stuffy nose.
  • Get skin infections.

Low Platelet Count

A low platelet count is called thrombocytopenia. If you have a low platelet count, you may:

  • Bruise or bleed more easily – even from minor scrapes and bumps.
  • Get heavy menstrual periods.
  • Get nose bleeds.
  • Get tiny, flat red spots under your skin, which are caused by bleeding. These spots are called petechiae.
  • Have bleeding gums, especially after dental work or from brushing your teeth. Check with your doctor before getting any dental work.

For more in-depth information on blood and bone marrow, view our Blood and Bone Marrow Basics Interactive Module.