Platelet Count

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Also known as: Thrombocyte count
Related tests: FBC, Platelet aggregation, Platelet Function Tests, Blood Film, von Willebrand Factor, HIT Antibody, Coagulation Factors, PT, aPTT, JAK2

At a Glance

Why Get Tested?

To count the number of platelets present in blood. This may be performed if there are symptoms of a bleeding disorder, an unexplained blood clot, or to check that the bone marrow is working as it should.

When to Get Tested?

The platelet count is performed as part of a full blood count (FBC) analysis, which may be carried out as a general screen during routine healthcare examinations or for the diagnosis or monitoring of diseases that affect the blood and bone marrow.

Sample Required?

A blood sample taken from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

Platelets are small cell fragments and are found in the blood along with red cells and white cells. Platelets are produced in the bone marrow and released into the blood where they play an important role in coagulation (blood clotting), helping to stop bleeding when blood vessels are injured. They are the first cells to be recruited to sites of injury and, when activated, they clump together (aggregate), sealing the blood vessel and forming a blood clot. These small, disc-shaped cells usually live for around 5-10 days in the blood before they are destroyed.

Platelets are very important for efficient blood coagulation and preventing unnecessary or excessive blood loss. If there are too few platelets, or if the platelets that are present don’t function properly, then there may be problems with blood clot formation. On the other hand, too many platelets can increase the risk of blood clots that can block blood vessels and cause organ damage.

The platelet count simply provides information on the number of these cells that are present in blood; it does not reveal if these cells are functioning properly. Specialised tests, called the platelet function tests, are used when there is suspicion of a platelet function defect.

How is the sample collected for testing?

The platelet count is performed on a sample of blood obtained from a vein in the arm using a needle. This is a process which may be referred to as ‘venepuncture’.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

Common Questions

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.