Platelet Count Test
Also known as: PLT, Thrombocyte Count
What is Platelet Count?
Platelets are small blood cell fragments that help blood clot to stop bleeding. The platelet count measures the number of platelets in your blood.[MedlinePlus (NIH)]
What This Test Measures
This test counts the number of platelets per microliter of blood. Platelets are essential for normal blood clotting.[Mayo Clinic]
Why It's Important
Platelet count helps diagnose bleeding disorders, bone marrow problems, and conditions that affect clotting.[MedlinePlus (NIH)]
Low platelets increase bleeding risk; high platelets can increase clotting risk.[Cleveland Clinic]
Who Should Get This Test?
Platelet count is routinely measured as part of a complete blood count.
Risk Factors
- Easy bruising or unexplained bleeding
- Prolonged bleeding from cuts or dental procedures
- Heavy menstrual periods
- Petechiae (tiny red spots under skin)
- History of blood clots
- Receiving chemotherapy or radiation
- Liver disease or cirrhosis
- Autoimmune conditions
Screening Schedule
Part of routine CBC; more frequent monitoring for those on blood thinners, chemotherapy, or with bleeding disorders.
What Happens During the Test
A blood sample is drawn from a vein in your arm. The sample is analyzed by an automated hematology analyzer that counts platelets using optical or impedance methods.
Duration
5-10 minutes for blood draw; results typically available same day
Discomfort Level
Minimal discomfort from needle insertion
Risks & Side Effects
Standard blood draw with minimal risks.
- •Brief pain at needle site
- •Small bruise may develop
- •Extended bleeding at puncture site if platelet count is very low
- •Very rare: infection at puncture site
Normal Range
150,000 to 400,000 platelets per microliter (mcL).
Note: Counts may temporarily change due to exercise, pregnancy, or altitude.
Source: MedlinePlus (NIH)Unit Conversion
Convert between platelets/mcL and ×10⁹/L
| platelets/mcL | ×10⁹/L |
|---|---|
| 100000 | 100 |
| 150000 | 150 |
| 250000 | 250 |
| 400000 | 400 |
| 600000 | 600 |
High Values
High platelet count (thrombocytosis) can be caused by infection, inflammation, iron deficiency, cancer, or bone marrow disorders. It may increase risk of blood clots.[Mayo Clinic]
Low Values
Low platelet count (thrombocytopenia) can cause easy bruising and bleeding. Causes include viral infections, autoimmune disorders, medications, leukemia, and chemotherapy.[Cleveland Clinic]
Test Limitations & Accuracy
Several factors can affect platelet count accuracy:
- ⚠Platelet clumping in the sample tube can cause falsely low counts
- ⚠Giant platelets may be miscounted as red blood cells
- ⚠Recent blood transfusion affects results
- ⚠High altitude living increases platelet counts
- ⚠Pregnancy normally decreases platelet counts slightly
- ⚠Strenuous exercise can temporarily elevate counts
- ⚠Some medications affect platelet production or destruction
Alternative & Complementary Tests
Additional tests may be ordered to evaluate platelet function:
To assess platelet size and production
To visually examine platelet appearance
To assess how well platelets work (PFA-100, aggregation studies)
When production problems suspected
To evaluate the clotting cascade along with platelet function
Frequently Asked Questions
What are symptoms of low platelets?
Symptoms include easy bruising, prolonged bleeding from cuts, spontaneous bleeding from gums or nose, blood in urine or stool, heavy menstrual periods, and petechiae (tiny red spots on skin).
Source: Mayo ClinicReferences
Related Condition Guides
Medical Disclaimer
This information is for educational purposes only and is not intended as medical advice. Always consult with a qualified healthcare provider for interpretation of test results and medical decisions.
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