A hematocrit (he-MAT-uh-krit) test measures the proportion of red blood cells in your blood. Red blood cells carry oxygen throughout your body. Having too few or too many red blood cells can be a sign of certain diseases. The hematocrit test, also known as a packed-cell volume (PCV) test, is a simple blood test. Platelets are blood cells that help your blood clot. It is usually done as a part of a Complete blood count. A normal platelet count range is between 150,000 - 400,000/microliter of blood. A low platelet count is indicative of certain cancers or infections. On the other hand, a high platelet count can put you at risk for stroke or blood clots.