Normal Platelet Count and the Causes of Low and High Platelet Count

Blood Platelets and their Functions

Platelets or thrombocytes are the smallest cells in the blood and designed for one important purpose – to initiate the process of coagulation, or blood clotting, whenever a blood vessel is broken. As soon as a vein or artery is broken, the platelets in the broken area begin to clump together and stick to the edges of the cut. In other words, the platelets work together to seal the injured area of the blood vessel to prevent bleeding.

The platelets also initiate the transformation of the plasma protein fibrinogen into fibrin, a long sticky protein that works with the platelets in creating blood clot to the injured area of the blood vessel. Moreover, the platelets release chemical messengers that initiate constriction of the blood vessels to reduce bleeding. The chemical messenger also attracts other platelets to the broken part of the blood vessel to assist in blood clotting.

By reducing and stopping blood loss in the event of blood vessel injury, blood platelets are important to human survival.                Diseases associated to platelets and blood clotting are deadly. It is therefore important to monitor the health of the platelets by ordering laboratory tests such as Platelet Count and Mean Platelet Volume (MPV).

What is Platelet Count Test?

Platelet count test is a part of a regular Complete Blood Count (CBC), a panel of laboratory tests that examine different components of the blood such as white blood cell (WBC) count, red blood cell (RBC) count, or mean platelet volume (MPV). Platelet count is a measure of the number of platelets in a given sample of blood. The test result is interpreted by a doctor to determine if a patient has bleeding disorders, bone marrow diseases (e.g. leukemia), and other health problems.

Platelet count test is also ordered by the doctor if a patient has unexplained bruises in his/her body and it takes an unusually long period of time to stop bleeding from a small cut or wound in the skin.

What is Normal Platelet Count?

Normal platelet count ranges from 150,000 to 450,000 platelets per microliter (X106/L) of adult blood. Platelet count that falls below 20,000 per microliter of blood can cause spontaneous bleeding which is life-threatening. There are different reasons why platelet count decreases (thrombocytopenia). One of these reasons is leukemia or cancer of the bone marrow. The bone marrow is the site of production of new platelets that would replace old and used platelets. Therefore, no new platelets are produced if normal bone marrow cells are transformed to cancer cells.

Decrease in platelet count does not only indicate leukemia but can also indicate underlying health conditions which are discussed below.

What Causes of Low Platelet Count?

  • Low platelet count (thrombocytopenia) is observed in patients with long-term bleeding problems like chronic stomach bleeding due to ulcer.
  • Decline in platelet count is seen in patients with gram-negative sepsis.
  • Low platelet count is also observed in patients with lupus erythematosus, a rare autoimmune disorder characterized by the production of antibodies that attack the patients’ platelets and other tissues and organs of their body.
  • Decreased platelet count is observed in cancer patients who undergone chemotherapy and radiation.
  • Certain drugs were found to lower platelet count such as acetaminophen, valium, digoxin, sulfa drugs, nitroglycerine, quinidine, and among others.
  • Sequestration of platelets in the spleen decreases the number of platelets that circulates around the body.
  • Platelet count decrease is observed in kidney diseases that cause thrombocytopenic urea and hemolytic uremic syndrome.
  • Women could have low platelet count before their menstruation.

What Causes High Platelet Count?

  • Increase in platelet count or thrombocytosis has been observed in people who don’t have any health problem. However, some people with platelet count increase could have disorders like myeloproliferative disorder, a bone marrow disease in which excess cells are produced.
  • There is an increase in platelet count after undergoing splenectomy or spleen removal.
  • Reactive thrombocytosis due to inflammatory diseases such as rheumatoid arthritis and inflammatory bowel disease could cause high platelet count.
  • Estrogen and oral contraceptives could cause high platelet count.
  • Living in high altitude can increase an individual’s blood platelets.
  • Heavy exercise also causes blood platelets to soar up.
  • People who have increased platelet count can still experience bleeding problem if their platelets do not stick together to create a blood clot that will plug a broken blood vessel.
  • Unregulated blood clotting and increase in platelets could result to throboembolism, wherein a blood clot blocks the flow of blood in a blood vessel. Thromboembolism in blood vessels that supply blood to the brain and heart muscles can cause death.


The information provided in this article should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical doctor should be consulted for diagnosis and treatment of any and all medical conditions.[ad#afterpost]


Platelet Count – Laboratory Test Online – American Association For Clinical Chemistry

Platelet Count – Medline Plus Medical Encyclopedia – National Institute of Health Website