Platelet count
Number of platelets, the blood cells needed for clotting, part of the blood count
Also known as
Definition
Platelets, also called thrombocytes, are small blood cells that form in the bone marrow. When you are injured, they stick together with proteins and other cells to form a clot and stop the bleeding. The platelet count shows how many platelets are in your blood and is part of the complete blood count. Platelet function tests are different: they check how well the platelets form a clot.
| Parameter | Value |
|---|---|
| Unit | ×10⁹/L (= /nL = ×10³/µL) |
| Reference Range | Typical for adults: 150 to 400 × 10⁹/L, which equals 150 to 400 /nL or 150,000 to 400,000 per µL. Labs differ slightly; the reference range on your own report is what counts. Discuss your result with your doctor. |
Agree on your personal target range with your doctor.
150 × 10⁹/L = 150 /nL = 150,000 /µL. US reports often use /mcL or ×10³/µL; German reports often use /nl.
↓ What a low value means
A platelet count below 150 × 10⁹/L is called thrombocytopenia. It may be related to the bone marrow making too few platelets or to platelets being broken down in the blood, the spleen or the liver. Possible links include chemotherapy or radiation, medicines, autoimmune diseases, viral infections, diseases of the bone marrow or blood, cirrhosis and vitamin B12 deficiency. A mostly mild form occurs during pregnancy. According to MedlinePlus, the risk of bleeding rises below 50 × 10⁹/L. Discuss any deviations with your doctor.
↑ What a high value means
A platelet count of 400 × 10⁹/L or above is called thrombocytosis. It may be related to iron deficiency, anemia, infections, severe blood loss, major surgery or injury, inflammatory diseases such as inflammatory bowel disease or rheumatoid arthritis, certain medicines, removal of the spleen, some cancers or bone marrow diseases. Very high values can go along with a tendency to form clots or even to bleed. Interpretation belongs with your doctor.
When to test
The platelet count is usually measured as part of a blood count at a routine checkup, and also with symptoms such as prolonged bleeding after small cuts, frequent nosebleeds, unexplained bruising or pinpoint red spots on the skin. No preparation is needed for the count itself.
Frequently asked questions
What is the difference between a platelet count and a platelet function test? +
The platelet count only shows how many platelets are in your blood. Function tests check how well the platelets clump together and form a clot. They are used specifically, for example when a platelet disorder is suspected or before major surgery.
Do I need to fast for the test? +
No special preparation is needed for a platelet count. Before a function test, you may be asked to pause certain medicines such as aspirin or ibuprofen. Only stop medicines after talking to your doctor.
What does a low platelet count during pregnancy mean? +
A common, mostly mild form of thrombocytopenia occurs during pregnancy. According to MedlinePlus, it is not known to harm mother or baby, and it usually improves on its own. Your doctor will interpret your result.
Why can very many platelets also lead to bleeding? +
Many platelets can increase the tendency to form clots. According to MedlinePlus, extremely high counts can also lead to excessive bleeding. What a high value means in your case is something to clarify with your doctor.
Platelet count
Sources
Last updated: October 05, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.