A platelet count is a lab test to measure how many platelets you have in your blood. Platelets are parts of the blood that help the blood clot. They are smaller than red or white blood cells.
Most of the time you do not need to take special steps before this test.
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.
The number of platelets in your blood can be affected by many diseases. Platelets may be counted to monitor or diagnose diseases, or to look for the cause of too much bleeding or clotting.
The normal number of platelets in the blood is 150,000 to 400,000 platelets per microliter (mcL) or 150 to 400 × 109/L.
Normal value ranges may vary slightly. Some labs use different measurements or may test different specimens. Talk to your doctor about your test results.
LOW PLATELET COUNT
A low platelet count is below 150,000 (150 × 109/L). If your platelet count is below 50,000 (50 × 109/L), your risk for bleeding is higher. Even every day activities can cause bleeding.
A lower-than-normal platelet count is called thrombocytopenia. Low platelet count can be divided into 3 main causes:
Three of the more common causes of this problem are:
If your platelets are low, talk to your health care provider about how to prevent bleeding and what to do if you are bleeding.
HIGH PLATELET COUNT
A high platelet count is 400,000 (400 × 109/L) or above.
A higher-than-normal number of platelets is called thrombocytosis. It means your body is making too many platelets. Causes may include:
Some people with high platelet counts may be at risk for forming blood clots or even bleeding too much. Blood clots can lead to serious medical problems.
There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another, and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight, but may include:
Cantor AB. Thrombocytopoiesis. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 7th ed. Philadelphia, PA: Elsevier; 2018:chap 28.
Chernecky CC, Berger BJ. Platelet (thrombocyte) count - blood. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders; 2013:886-887.
Schafer AI. Approach to the patient with bleeding and thrombosis. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 162.
Reviewed By: Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.