Platelet Count Blood Test

This test counts the number of platelets in a microliter of your whole blood, reported in thousands per microliter. It measures how many platelets you have, not how well they work: platelet function is assessed with different tests.

People re-checking a previous low or high platelet count; people whose clinician is following platelets over time; and people with a known condition that affects platelets. If you are noticing unexplained bruising, nosebleeds or tiny red skin spots for the first time, a full CBC is the better starting point, and new or heavy bleeding should be checked by a clinician promptly rather than waiting for a self-ordered test.

Any time of day, with no fasting. Infections, including viral illnesses, can change the count, so if you are re-checking a value, ask your clinician about timing.

Quest's reference range for adults and children over 6 months is 140-400 thousand per microliter. A low count (thrombocytopenia) may be linked to viral infections such as mononucleosis or hepatitis, autoimmune disease, cirrhosis, vitamin B12 deficiency, bone marrow damage or blood cancers, and a mild drop is common in pregnancy. A high count (thrombocytosis) may come with infection, inflammation such as rheumatoid arthritis or inflammatory bowel disease, anemia, severe blood loss and, less often, certain cancers. Quest notes that a difficult draw or refrigeration can trap platelets in the sample, one reason an unexpected result is often repeated. Review your result with a clinician; a very low count, or any count with unusual bleeding, needs prompt medical attention. JustLabs results are informational and do not replace medical care.