Testing.com is fully supported by readers. We may earn a commission through products purchased using links on this page. You can read more about how we make money here.

  • Also Known As:
  • PLT
  • PLT Count
Medically Reviewed by Expert Board

This page was fact checked by our expert Medical Review Board for accuracy and objectivity. Read more about our editorial policy and review process.

.
This article was last modified on
Learn more about...
  • computer screen
    Select, schedule, and purchase your test

    It’s simple and conveniently online

  • labcoat
    Visit a Quest Patient Service Center for your appointment

    Choose from more than 2,200 locations nationwide

  • mobile phone
    Get your confidential results sent directly to you

    Access your results online via the secure MyQuest™ portal

Test Quick Guide

The platelet count test is a lab test which measures the number of platelets you have in your blood. Platelets, also known as thrombocytes, are tiny, round cell fragments which circulate in your blood and are essential for the formation of blood clots. A blood clot is a mass of blood that the body forms in order to stop bleeding.

Platelets are one of three main components of the blood along with red blood cells and white blood cells.

Platelet count testing can detect when platelet levels are too low or too high. Low platelet levels make it difficult for the body to form blood clots, which can cause excessive bleeding. High platelet levels can cause too much clotting. Blood clots in the blood vessels can become lodged in the lungs, intestines, brain or heart, and this can result in serious medical conditions.

About the Test

Purpose of the test

The purpose of a platelet count test is to assess your blood’s ability or inability to clot. While platelet counts are often included on multi-test panels such as the complete blood count, this test can also be done on its own.

The platelet count may be conducted by your doctor as part of routine blood testing. Platelet counts are also ordered to:

  • Diagnose a platelet disorder
  • Assess risk of bleeding before surgery
  • Monitor you during medical treatments such as blood thinners or chemotherapy.

The platelet count is used to diagnose disease and to help determine the cause of excess bleeding or clotting. Both high platelet counts and low platelet counts can have associated risks that can range from either not causing any noticeable health problems to being very serious and life-threatening.

A platelet count test is also used to monitor patients who have been diagnosed with a clotting condition. Regularly conducting a platelet count allows doctors to check the effectiveness of medications that increase or decrease the blood’s ability to form a clot.

What does the test measure?

The platelet count measures the number of platelets in your sample of blood. The results are reported as a number of platelets per microliter. The number of platelets in your blood is important in determining the blood’s ability to form a blood clot as well as your body’s ability to form the cells that become platelets. These functions can be affected by disease or medication therapy.

Measuring a platelet count typically involves analyzing a blood sample using automated laboratory technology. In some cases, automated results need to be confirmed using a peripheral blood smear, which is a method of manually measuring the number of platelets in a blood sample.

When should I get a platelet count test?

Your doctor may recommend that you take a platelet count test during a check up as part of a broader screening panel such as a complete blood count. Your doctor might also recommend platelet count testing if you have symptoms that are associated with abnormal platelet levels. Low or high platelet counts may or may not cause signs and symptoms. It’s important to speak with your doctor anytime you notice concerning health changes.

Symptoms of low platelets levels

Bleeding is the main sign and symptom of a low platelet count. Early signs of a low platelet count and can occur in any part of the body and may include but are not limited to:

  • Bruising that is purple, reddish, or brown, occurring easily and often
  • Small red and purple dots on the skin
  • Abnormally prolonged bleeding, including from minor cuts
  • Bleeding from the nose or mouth
  • Atypically heavy vaginal bleeding, especially during menstruation
  • Excessive bleeding during dental work, including flossing, or surgery
  • Blood in the urine or stool, or bleeding from the rectum

Symptoms of high platelet levels

Signs of high platelet levels are primarily related to blot clots and bleeding. They may include:

  • Weakness or dizziness
  • Unexpected headache
  • Chest pain
  • Tingling of the hands and feet
  • Pain, swelling, warmth, and/or tenderness in one or both of the lower extremities

In some instances extremely high platelet counts may result in signs and symptoms that mirror low platelet counts. This occurs because too many clots have formed in the body and there are not enough platelets left to clot breaks in blood vessels. These signs and symptoms include:

  • Bleeding from many sites of the body at once
  • Shortness of breath
  • Confusion and changes in memory or behavior
  • Fever

Monitoring platelet levels

Your health care provider may also order a platelet count test when monitoring other health conditions. If you have been diagnosed with a disease that puts you at risk for high or low platelets, or if you have had abnormal results on platelet count tests in the past, your doctor may test you for platelet levels periodically. This allows your doctor to monitor your overall health and assess the effectiveness of treatment.

Finding a Platelet Count Test

How to get tested

Typically, a platelet count test is done by a licensed professional in a health care setting using a blood sample. The test can be conducted on its own or as part of a complete blood count test that is done in a doctor’s office, clinic, laboratory, or hospital.

A platelet count test is normally prescribed by a doctor. Talk with your health care provider if you have symptoms that could be related to abnormal platelet levels or if you are interested in a platelet count test.

Can I take the test at home?

Currently there are no at-home testing options available for the platelet count. Platelet counts are conducted by a medical professional and analyzed by a laboratory from a blood draw sample in a health care setting.

How much does the test cost?

The cost of a platelet count test depends on whether or not you have insurance and if that insurance plan covers the test. Some other factors that affect the cost are the setting of the blood draw and the lab to which the sample is sent.

For details on the expected cost for a platelet count that you may be responsible for, check with your doctor or insurance provider about any associated copays or deductibles.

Taking a Platelet Count Test

The platelet count test requires a blood sample ordered by a doctor that is collected in a medical setting by a licensed professional, such as a phlebotomist.

Before the test

Special preparation is not required prior to a platelet count test unless specified by your health care provider. Your health care provider may order the platelet count by itself, as part of the complete blood count, or along with other blood tests.

If you are receiving more than one blood test, your provider may ask you to not eat anything for a certain amount of time prior to your test. If you have questions or concerns about any test preparation, contact your health care provider for detailed instructions.

During the test

A blood sample for a platelet count is taken from a vein in your arm or from your forearm by a health care professional trained in drawing blood called a phlebotomist. The phlebotomist will tie a tourniquet around the upper part of your arm to increase the blood pressure in the vein of your arm so it is easier to find. They will cleanse your skin around the area of the vein with an antiseptic wipe. They will then insert a needle to draw blood from the vein. They will then attach a vacuum tube on the needle to help pull blood from the vein and, if drawing blood for multiple tests, they may attach several different tubes.

There may be a brief stinging sensation when the needle is initially inserted into your arm. This pain usually does not last long, and the test itself can be completed in under one minute.

After the test

After the procedure is complete, the phlebotomist will apply folded gauze and a bandaid over the site to reduce bleeding, remove the tourniquet, and remove the needle.

The main risk associated with blood draws is local bruising at the site of the needle puncture. This bruising may last longer than usual if you are experiencing low platelets. Because low platelet counts reduce the clotting potential of your blood it may be suggested to keep the bandage on for a specified period of time.

The phlebotomist may ask you to stay at the facility for a few minutes so they can monitor you for dizziness before returning to normal activities including walking and driving.

Platelet Count Test Results

Receiving test results

The results from a platelet count can be available in a few minutes to a few days after the blood sample arrives at the laboratory depending on the laboratory equipment that is used.

If not available immediately, a copy of your results may be sent to you by mail or through an electronic health portal. It is also possible that your health care provider may also call you to discuss the results, retest, or to schedule an appointment to review them together.

Interpreting test results

Test results are interpreted in comparison with the test reference range. The reference range is the results range that is considered to be a normal result. Platelet test results that fall outside of the reference range indicate that platelet levels may be too low or too high.

The reference range for platelet counts gives a wide range of normal results. This reflects the range in platelet levels that allows most people to function without adverse health issues. Specific reference ranges vary from one laboratory to the next, and your results are considered in context of your overall health risk factors.

The American Board of Internal Medicine lists a typical platelet count reference range as 150,000 to 450,000 per microliter.

Platelet counts tend to be slightly higher in certain populations, including:

  • Females
  • Younger people when compared with older people
  • Non-Hispanic Black individuals when compared with White individuals.

Your doctor may consider retesting if you have significant decreases or increases in your platelet numbers from one test to the next even if they are within normal range as this may indicate a potential problem.

If you have a platelet count test result that is lower than expected, your doctor will consider whether another condition may be causing or contributing to a decrease in platelets. Some causes and risk factors associated with low platelet counts are:

  • Certain cancers
  • Aplastic anemia
  • Autoimmune diseases and conditions
  • Certain medications
  • Viral or bacterial infections
  • Genetic condition
  • Heavy alcohol use
  • Pregnancy

Other conditions can cause or increase risk for high platelet counts:

  • Rare genetic conditions
  • Bone marrow conditions
  • Certain cancers
  • Iron deficiency or hemolytic anemia
  • Inflammatory disease
  • Infections such as tuberculosis
  • Adverse medication reactions
  • Severe blood loss
  • Recovery from low blood platelet counts caused by heavy alcohol use or vitamin B12 or folate deficiency
  • Physical activity

Are test results accurate?

The platelet count test is a common test that is generally accurate; however, as with any laboratory test, there are some factors that can affect test accuracy.

Most platelet count tests are performed in a laboratory using automated instruments, which are designed to “flag” potential inaccuracies in the results. If your platelet count results indicate a possible inaccuracy, your test may be repeated using a peripheral blood smear. Rather than using automated instruments, a peripheral blood smear involves having your blood sample viewed under a microscope by a trained laboratory professional.

In some cases, platelets may clump together resulting in falsely low platelet counts. Some genetic disorders that cause platelets to be larger than normal may also result in low platelet counts. In other instances, abnormal shapes of red blood cells and/or white blood cells result in abnormal platelet counts.

Do I need follow-up tests?

Depending on the results of your platelet count test, it is possible that your doctor will order follow up tests to learn more about your overall health. Commonly ordered follow up tests include:

  • Complete blood count: If your platelet count does not match the context of your symptoms and other test results, your doctor may reorder a complete blood count panel to confirm the results prior to more extensive evaluations or interventions.
  • Peripheral blood smear: Automated blood count instrumentation is most often used to measure blood counts, including platelet counts. A peripheral blood smear involves manually analyzing the blood sample under a microscope and can be used to confirm an abnormal result on an automated platelet count.
  • HIV or HCV test: Low platelet counts are often seen in people who have human immunodeficiency virus (HIV) or Hepatitis C virus (HCV) infection. Follow up testing may be used to rule out or confirm the existence of HIV or HCV as the cause of low platelets.

Other tests may be conducted to diagnose the cause of abnormal platelets. Testing depends on the specific conditions that are suspected. If you receive an abnormal platelet count result, your doctor can help you understand what follow up testing is recommended for you and why.

Questions for your doctor about test results

It may be helpful to ask your doctor the following questions about your platelet count results:

  • Was my test result abnormal? If so, was it abnormally high or low?
  • What does my platelet count indicate about my health?
  • Are there any diagnoses to be made based on my platelet count results?
  • Will any follow up tests be needed?
  • Will I be prescribed medication based on my results?

Related Tests

Platelet count test vs. platelet function test

A platelet count test strictly counts the platelets in your blood, whereas a platelet function test analyzes the functionality of your platelets including:

  • The time it takes for your platelets to plug a small hole
  • The strength of the clot
  • The ability for your platelets to clump together or “aggregate”
  • Any possible platelet defects
  • Screening for abnormalities such as protein on your platelets, which may indicate a platelet disorder
  • The amount of time that it takes a small cut to stop bleeding, though newer and more reliable tests are more often used to determine platelet dysfunction.

Platelet count vs. mean platelet volume test

A platelet count is often conducted as one of a series of tests that are included in a complete blood count (CBC). A  mean platelet volume (MPV) is another test that may also be included as part of a CBC panel. Platelet counts reflect the number of platelets in your blood sample, while  an MPV measures the average size of your platelets. An MPV is helpful in diagnosing bleeding disorders and bone marrow conditions.

Platelet count test vs. other coagulation tests

The number of platelets you have isn’t the only factor that affects clot formation, also called coagulation. There are a few other tests that provide information on your body’s ability to form blood clots. A partial thromboplastin time (PTT) test and a prothrombin time and international normalized ratio (PT/INR) test measure the amount of time that it takes your blood to form a clot.

Testing for levels of proteins C and S can indicate how your body regulates clot formation. While platelets help your body form clots, proteins C and S help prevent your blood from clotting too much. Without these proteins, you may end up with blood that clots partially or completely block the blood flow in a vein or artery.

View Sources

A.D.A.M. Medical Encyclopedia. Disseminated intravascular coagulation (DIC). Updated September 24, 2019. Accessed October 3, 2021. https://medlineplus.gov/ency/article/000573.htm

A.D.A.M. Medical Encyclopedia. Pulmonary embolus. Updated September 24, 2019. Accessed October 3, 2021.https://medlineplus.gov/ency/article/000132.htm

A.D.A.M. Medical Encyclopedia. CBC blood test. Updated October 16, 2020. Accessed October 3, 2021. https://medlineplus.gov/ency/article/003642.htm

A.D.A.M. Medical Encyclopedia. Platelet count. Updated January 19, 2021. Accessed October 3, 2021. https://medlineplus.gov/ency/article/003647.htm

A.D.A.M. Medical Encyclopedia. Protein C blood test. Updated January 19, 2021. Accessed October 3, 2021.https://medlineplus.gov/ency/article/003659.htm

American Board of Internal Medicine. ABIM laboratory test reference ranges ̶ July 2021. Updated July 2021. Accessed October 3, 2021. https://www.abim.org/Media/bfijryql/laboratory-reference-ranges.pdf

American Society of Clinical Oncology. Low platelet count or thrombocytopenia. Published August 20200. Accessed October 13, 2021. ​​https://www.cancer.net/coping-with-cancer/physical-emotional-and-social-effects-cancer/managing-physical-side-effects/low-platelet-count-or-thrombocytopenia

Arnold DM, Cuker A. Diagnostic approach to the adult with unexplained thrombocytopenia. In: Leung LLK, ed. UpToDate. Updated May 18, 2021. Accessed October 3, 2021. https://www.uptodate.com/contents/diagnostic-approach-to-the-adult-with-unexplained-thrombocytopenia

Bauer KA, Huisman MV. Clinical presentation and diagnosis of the nonpregnant adult with suspected deep vein thrombosis of the lower extremity. In: Leung LLK, Mandel J, Muller NJ eds. UpToDate. Updated July 20, 2021. Accessed October 3, 2021 https://www.uptodate.com/contents/clinical-presentation-and-diagnosis-of-the-nonpregnant-adult-with-suspected-deep-vein-thrombosis-of-the-lower-extremity

Blumberg N, Heal JM, Phillips GL. Platelet transfusions: trigger, dose, benefits, and risks. F1000 Med Rep. 2010;2:5. Published 2010 Jan 27. doi:10.3410/M2-5

Coutre S. Congenital and acquired disorders of platelet function. In: Leung LLK, ed. UpToDate. Updated August 23, 2019. Accessed October 3, 2021. https://www.uptodate.com/contents/congenital-and-acquired-disorders-of-platelet-function

Editorial Staff. Overview of blood. Merck Manuals Consumer Edition. Updated April 2020. Accessed October 3, 2021. https://www.merckmanuals.com/home/quick-facts-blood-disorders/biology-of-blood/overview-of-blood

George JN, McIntosh JJ. Thrombocytopenia in pregnancy. In: Leung LLK, Lockwood CJ eds. UpToDate. Updated March 19, 2021. Accessed October 3, 2021 https://www.uptodate.com/contents/thrombocytopenia-in-pregnancy

George TI. Automated hematology instrumentation. In: Uhl L, ed. UpToDate. Updated June 3, 2021. Accessed October 3, 2021. https://www.uptodate.com/contents/automated-hematology-instrumentation

Harrison P. Platelet function testing. In: Leung LLK, ed. UpToDate. Updated September 30, 2021. Accessed October 15, 2021. https://www.uptodate.com/contents/platelet-function-testing

Kuter DJ. Overview of platelet disorders. Merck Manuals Consumer Edition. Updated July 2020. Accessed October 3, 2021. https://www.merckmanuals.com/home/blood-disorders/platelet-disorders/overview-of-platelet-disorders

Kuter DJ. Overview of thrombocytopenia. Merck Manuals Consumer Edition. Updated July 2020. Accessed October 3, 2021. https://www.merckmanuals.com/home/blood-disorders/platelet-disorders/overview-of-thrombocytopenia

Kuter DJ. Megakaryocyte biology and the production of platelets. In: Leung LLK, ed. UpToDate. Updated April 22, 2021. Accessed October 3, 2021.  https://www.uptodate.com/contents/megakaryocyte-biology-and-the-production-of-platelets

Kuter DJ. Biology and physiology of thrombopoietin. In: Leung LLK, ed. UpToDate. Updated July 19, 2021. Accessed October 3, 2021. https://www.uptodate.com/contents/biology-and-physiology-of-thrombopoietin

Kuter DJ. Laboratory tests for blood disorders. Merck Manuals Consumer Edition. Updated July 2021. Accessed October 3, 2021. https://www.merckmanuals.com/home/blood-disorders/symptoms-and-diagnosis-of-blood-disorders/laboratory-tests-for-blood-disorders

Leung LLK. Overview of hemostasis. In: Mannucci PM, ed. UpToDate. Updated October 1, 2019. Accessed October 3, 2021. https://www.uptodate.com/contents/overview-of-hemostasis

Liesveld J. Essential Thrombocythemia. Merck Manuals Consumer Edition. Updated September 2020. Accessed October 3, 2021. https://www.merckmanuals.com/home/blood-disorders/myeloproliferative-disorders/essential-thrombocythemia

Liu YT. How To Do Venous Blood Sampling. Merck Manuals Professional Edition. Updated October 2020. Accessed October 3, 2021. https://www.merckmanuals.com/professional/critical-care-medicine/how-to-do-peripheral-vascular-procedures/how-to-do-venous-blood-sampling

MedlinePlus: National Library of Medicine. Blood thinners. Updated April 2, 2021. Accessed October 3, 2021. https://medlineplus.gov/bloodthinners.html

MedlinePlus: National Library of Medicine. Complete blood count CBC Updated July 31, 2020. Accessed October 3, 2021. https://medlineplus.gov/lab-tests/complete-blood-count-cbc

MedlinePlus: National Library of Medicine. Coagulation factor tests. Updated November 30, 2020. Accessed October 3, 2021. https://medlineplus.gov/lab-tests/coagulation-factor-tests/

MedlinePlus: National Library of Medicine. MPV blood test. Updated July 31, 2020. Accessed October 3, 2021. https://medlineplus.gov/lab-tests/mpv-blood-test

MedlinePlus: National Library of Medicine. Partial thromboplastin time PTT test. Updated December 10, 2021. Accessed October 3, 2021. https://medlineplus.gov/lab-tests/partial-thromboplastin-time-ptt-test/

MedlinePlus: National Library of Medicine. Platelet tests. Updated February 18, 2021. Accessed October 3, 2021. https://medlineplus.gov/lab-tests/platelet-tests/

MedlinePlus: National Library of Medicine. Protein C and protein S tests. Updated December 3, 2020. Accessed October 3, 2021. https://medlineplus.gov/lab-tests/protein-c-and-protein-s-tests/

MedlinePlus: National Library of Medicine. Prothrombin time test and INR (PT/INR). Updated September 16, 2021. Accessed October 3, 2021. https://medlineplus.gov/lab-tests/prothrombin-time-test-and-inr-ptinr/

National Cancer Institute. Dictionary of Cancer Terms: Peripheral blood smear. Date unknown. Accessed October 3, 2021. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/peripheral-blood-smear

National Heart, Lung, and Blood Institute. Stroke. Date unknown. Accessed October 3, 2021. https://www.nhlbi.nih.gov/health-topics/stroke

National Heart, Lung, and Blood Institute. Thrombocythemia and Thrombocytosis. Date unknown. Accessed October 3, 2021. https://www.nhlbi.nih.gov/health-topics/thrombocythemia-and-thrombocytosis

National Heart, Lung, and Blood Institute. Thrombocytopenia. Date unknown. Accessed October 3, 2021. https://www.nhlbi.nih.gov/health-topics/thrombocytopenia

National Heart, Lung, and Blood Institute. Venous thromboembolism. Date unknown. Accessed October 3, 2021. https://www.nhlbi.nih.gov/health-topics/venous-thromboembolism

Raber MN. Coagulation tests. In: Walker HK, Hall WD, Hurst JW, editors. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Boston: Butterworths; 1990. Chapter 157. Available from: https://www.ncbi.nlm.nih.gov/books/NBK265/

Rosenthal DS. Evaluation of the peripheral blood smear. In: Brodsky RA, ed. UpToDate. Updated May 17, 2021. Accessed October 3, 2021. https://www.uptodate.com/contents/evaluation-of-the-peripheral-blood-smear

Sahler J, Grimshaw K, Spinelli SL, Refaai MA, Phipps RP, Blumberg N. Platelet storage and transfusions: new concerns associated with an old therapy. Drug Discov Today Dis Mech. 2011;8(1-2):e9-e14. doi:10.1016/j.ddmec.2011.06.001

Tefferi A. Approach to the patient with thrombocytosis. In: Leung LLK, ed. UpToDate. Updated May 18, 2021. Accessed October 3, 2021. https://www.uptodate.com/contents/approach-to-the-patient-with-thrombocytosis

Tefferi A, Barbui T. Polycythemia vera and essential thrombocythemia: 2021 update on diagnosis, risk-stratification and management. Am J Hematol. 2020;95(12):1599-1613. doi:10.1002/ajh.26008

Ask a Laboratory Scientist

Ask a Laboratory Scientist

This form enables patients to ask specific questions about lab tests. Your questions will be answered by a laboratory scientist as part of a voluntary service provided by one of our partners, American Society for Clinical Laboratory Science. Please allow 2-3 business days for an email response from one of the volunteers on the Consumer Information Response Team.

Send Us Your Question