Platelets are small, round colorless blood cells that allow your blood to clot to prevent bleeding. Of the three major blood cell types, including white blood cells and red blood cells, platelets are the smallest but most numerous cell in the blood. Large bone marrow cells called megakaryocytes produce platelets at a rate of 1,000 platelets per megakaryocyte.
Function of Platelets
Platelets are the small and lightest of the blood cells. The rapid flow of blood pushes them from the center of flowing blood to the wall of the blood vessel. When an injury or cut occurs, platelets clump together at the site of the tear in the blood vessel. This clump seals the hole in the blood vessel preventing blood loss.
Platelet Count
The platelet count is an actual and precise count of the number of platelets per cubic milliliter of blood. Healthy platelets levels vary based on age. A healthy platelet level for an adult is 150,000 to 400,000 mm3, for a child 150,000 to 400,000 mm3, for an infant 200,000 to 475,000 mm3, for a premature infant 100,000 to 300,000 mm3 and for a newborn 150,000 to 300,000 mm3. Discuss the meaning of your specific test results with your doctor or health-care provider.
Reasons to Check a Platelet Count
Many diseases and conditions can affect your platelet count. A platelet count may be used to monitor or diagnose diseases or identify the cause of excessive bleeding. Anyone who develops petechia, or small hemorrhages in the skin, spontaneous bleeding or an increasingly heavier menstrual period should have a platelet count. Consult your physician or health-care provider immediately if you develop any of these conditions.
Abnormal Platelet Counts
A low platelet count, or thrombocytopenia, occurs when the level is below normal. Possible causes of a low platelet count include chemotherapy for cancer, infection, a vitamin B-12 deficiency, a genetic disorder, blood loss or leukemia. A high platelet count, or thrombocytosis, occurs when the level is above normal. Possible causes of a high platelet count include cancer, removal of the spleen, rheumatoid arthritis or iron-deficiency anemia. Always consult your doctor or health-care provider first for further testing.
References
- Platelets on the Web: Platelets
- "Mosby's Manual of Diagnostic and Laboratory Tests"; Kathleen Deska Pagana, PhD, RN and Timothy J. Pagana MD, FACS; 2006
- MayoClinic.com: Thrombocytopenia (Low Platelet Count)
- New York Times Health Guide: Platelet Count
