About Platelets

Blood platelets were first discovered in the mid- 1800s. We now know that they help make the blood clot, an important function of blood. Platelets are formed in the bone marrow. They are irregular in shape and are colorless. Normally, the body has between 150,000 and 400,000 per cubic millimeter. The normal life span of a platelet is 8-10 days and then it gets discarded through the spleen. If the spleen does not work normally or is absent, the platelet count increases, whereas over-activity of the spleen may cause a low platelet count.

Platelets are activated when the lining of the blood vessel is damaged. The platelets stick together and along with fibrin form a plug or clot. Formation of clots is important to stop bleeding. Everyone is familiar with a clot that forms on the skin's surface, a scab. Calcium and vitamin K must be present for the clots to form. If the levels of calcium and vitamin K are abnormally low, then blood takes longer to clot.

Some medications inhibit platelet function and are called "anti-platelets." Three common examples are aspirin, clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen. Other less common drugs also affect platelet function. Many diseases either elevate or reduce the number of circulating platelets and increase the risk of bleeding or clotting. Some diseases affect the adhesion or aggregation (clumping together) of platelets.

Platelets are tiny, but they are an essential part of clots to stop bleeding in the body.