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).
Normal value ranges may vary slightly. Some lab 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. If you do not have enough platelets, you may bleed too much.
If your platelet count is below 50,000, your risk of bleeding is much higher. Even every day activities can cause bleeding. If your platelets are low, you need to know how to prevent bleeding and what to do if you are bleeding.
A lower-than-normal platelet count is called thrombocytopenia. Low platelet count can be divided into 3 main causes:
3 of the more common causes of this problem are:
HIGH PLATELET COUNT
A high platelet count is 400,000 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 of forming blood clots. Blood clots can lead to serious medical problems
Veins and arteries vary in size so it may be harder to take a blood sample from one person than another.
Other slight risks from having blood drawn may include:
Cantor AB. Thrombocytopoiesis. In: Hoffman R, Benz EJ Jr, Silberstein LE, Heslop HE, Weitz JI, Anastasi J, eds. Hematology: Basic Principles and Practice. 6th ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 26.
Miller JL, Rao AK. Blood platelets and von Willebrand disease. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 40.
Reviewed By: Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.