Platelets are tiny, disc-shaped blood cells that circulate in the bloodstream. Their primary role is to form clots, preventing excessive blood loss and responding to injury.
What are Platelets and Why Are They Important?
Platelets are produced in the bone marrow from larger cells called megakaryocytes. Once released into the bloodstream, they typically have a lifespan of about 7 to 10 days before being removed, primarily by the spleen and liver. The body constantly produces around 100 billion platelets daily to maintain a consistent supply.
Platelets facilitate hemostasis, the process of stopping bleeding. When a blood vessel is damaged, platelets adhere to the injury site and aggregate, forming a temporary plug to seal the wound. They also activate other clotting factors in the blood, leading to the formation of a stable blood clot. This response prevents excessive bleeding from even minor cuts and bruises.
Understanding Critical Platelet Counts
A healthy platelet count in adults ranges from 150,000 to 450,000 platelets per microliter of blood. Variations outside this range can indicate underlying health concerns.
Critically low platelet counts, known as thrombocytopenia, occur when levels fall below 150,000 per microliter. Counts below 50,000 per microliter can lead to mild symptoms, while levels under 20,000 per microliter significantly increase the risk of spontaneous bleeding or severe hemorrhage.
Conversely, critically high platelet counts, known as thrombocytosis, are characterized by levels exceeding 450,000 platelets per microliter. While many people with elevated counts do not experience symptoms, counts above 1,000,000 per microliter can increase the risk of abnormal blood clotting (thrombosis). These clots can obstruct blood flow and cause complications.
Causes and Symptoms of Abnormal Platelet Counts
Low platelet counts can arise from various factors, including the bone marrow not producing enough platelets, or the body destroying or using them up too quickly. Common causes include bone marrow disorders like leukemia or aplastic anemia, autoimmune conditions such as immune thrombocytopenia (ITP), and certain infections like dengue or sepsis. Some medications, including certain antibiotics and the blood thinner heparin, can also lead to reduced platelet levels. Liver disease and excessive alcohol consumption are additional contributing factors.
Symptoms of low platelets often become noticeable when counts are very low. These can include easy bruising, the appearance of small red spots called petechiae, or larger purple patches known as purpura on the skin. Other signs may involve frequent nosebleeds, bleeding from the gums, prolonged bleeding from minor cuts, and blood in the urine or stool. Heavy or prolonged menstrual bleeding can also occur.
High platelet counts can be caused by underlying medical problems, such as infections, inflammation, or significant blood loss. Iron deficiency anemia, hemolytic anemia, and the removal of the spleen are also known contributors. In some instances, certain blood cancers, like essential thrombocythemia or other myeloproliferative neoplasms, can lead to uncontrolled platelet production.
While many individuals with high platelet counts have no symptoms, those who do may experience headaches, dizziness, or weakness. Vision changes, burning or tingling sensations in the hands and feet, and signs of blood clots like pain, swelling, or redness in a limb can also occur. In less common scenarios, very high platelet levels can paradoxically lead to bleeding, manifesting as nosebleeds, bruising, or bleeding from the mouth or gums.
Managing Abnormal Platelet Counts
Diagnosing abnormal platelet counts begins with a complete blood count (CBC), a blood test that measures platelet levels and other blood components. If an abnormality is detected, a healthcare provider may order additional tests, such as a peripheral blood smear to examine platelets under a microscope, or a bone marrow biopsy to assess the bone marrow’s health and determine the underlying cause.
Treatment for low platelet counts involves addressing the root cause of the condition. In cases of severe bleeding or extremely low counts, platelet transfusions may be administered to temporarily increase platelet levels. Medications like corticosteroids can be prescribed to reduce platelet destruction by the immune system, or thrombopoietin receptor agonists may be used to stimulate the bone marrow to produce more platelets. For certain autoimmune conditions, surgical removal of the spleen (splenectomy) might be considered if other treatments are ineffective, as the spleen can sometimes trap or destroy platelets.
Managing high platelet counts focuses on treating the underlying condition responsible for the elevation. For reactive thrombocytosis, platelet levels return to normal once the underlying cause, such as an infection or inflammation, resolves. In some situations, a daily low-dose aspirin may be recommended to reduce the risk of blood clots.
For conditions like essential thrombocythemia, medications such as hydroxyurea or anagrelide may be prescribed to lower platelet production in the bone marrow. In emergencies where very high platelet levels pose a threat of blood clots, a procedure called plateletpheresis can rapidly filter excess platelets from the blood. Consult a healthcare professional, especially a hematologist, for proper evaluation and management of abnormal platelet counts.