A platelet count is a test that measures the number of platelets in your blood. Platelets are cells that help your blood clot. Too few platelets can be a sign of cancer, infections or other health problems. Too many platelets put you at risk for blood clots or stroke. There are tens of thousands of platelets in a single drop of blood.
A platelet count is a quick, common test that measures how many platelets are in your blood. Platelets, or thrombocytes, are tiny blood cells that bud from cells in the bone marrow (megakaryocytes). Platelets form clots when there’s damage to a blood vessel. For example, if you cut your finger, platelets mix with clotting factors (proteins in the blood). Together, they form a “glue” that stops the bleeding. There are tens of thousands of platelets in a single drop of blood.
A platelet count is usually part of a complete blood count. This test measures the number of platelets, white blood cells and red blood cells. The bone marrow makes blood cells.
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Your healthcare provider may order a platelet count during a routine physical examination. Or they may do the test if they think you have:
Most people don’t need to do anything to prepare for a platelet count. In some cases, your healthcare provider may want you to fast (not eat or drink) before the test. Be sure to ask your provider if there are any instructions you should follow or medications to avoid before your blood test.
The process to get blood for a platelet count only takes a few minutes. You may get the test at your healthcare provider’s office, a hospital or a lab. A provider called a lab technician usually takes blood samples.
The lab technician:
A healthcare provider puts the blood in a small machine. The machine counts the platelets and other blood cells in about one minute.
In some cases, your provider may do a blood smear. This is an additional test to examine a small sample of blood under a microscope. A blood smear assesses the size and shape of blood cells.
A platelet count is a simple, common test. There are no significant risks. There may be a small amount of bleeding where the needle went into your vein. You might also see some light bruising or feel soreness on the inside of your arm.
Some people feel nervous around needles or before they have their blood drawn. This is natural. Try to breathe deeply to relax yourself during the test. It may help to look away from the needle as your blood is being drawn. You can also talk to someone during the test to distract yourself.
You may receive your results the same day as your blood test. Or you may need to wait about a week. Ask your healthcare provider when you can expect your results.
Platelets are measured per microliter of blood:
Low platelets can prevent blood from clotting. This could be a result of:
Symptoms of too few platelets include:
A high platelet count can cause too much clotting in your blood vessels. Or it can cause too much bleeding if the platelets interfere with clotting. It could be a sign of:
Symptoms and complications of too many platelets include:
A note from Cleveland Clinic
A platelet count is a quick, common test that counts the number of platelets in your blood. Platelets are cells that help your blood clot. A low platelet count might be a sign of certain cancers or infections. A high platelet count can put you at risk for harmful blood clots or stroke.
Last reviewed by a Cleveland Clinic medical professional on 09/08/2021.
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