Mean Platelet Volume or shortly MPV is a blood test that measures the average size of your platelets. Platelets, or thrombocytes, are the smallest cells in your blood. Their main role is to form clots and stop bleeding. Whenever there is damage in a blood vessel, platelets will move to the site of the injury and spread across the damaged surface by sticking to one another to stop the bleeding. Since older platelets are smaller in size than younger ones, MPV is also a reflection of how old the platelets might be. MPV is a test performed to help find and diagnose any bleeding disorders or bone marrow diseases, even if your platelet count is normal.  

High MPV levels are usually an indication that the platelets in your blood are bigger and younger. It might be related to thrombocytopenia, in which platelet levels in your body are lower than normal. An elevation of MPV is associated with leukemia, diabetes, hyperthyroidism, and heart disease. Pregnant women, facing pre-eclampsia, which is a complication causing high blood pressure, also have elevated MPV levels. 

Low MPV levels are usually an indication that the platelets in your blood are smaller and older. Low MPV levels are connected to bone marrow disorders, where the production of cells is decreased, such as aplastic anemia. A decrease in MPV can also be related to splenomegaly, in which the spleen is enlarged and traps the platelets in it, to hypothyroidism, lupus, or iron deficiency anemia. The drugs that are harmful to cells that suppress platelet formation, such as chemotherapy, can cause MPV levels to drop.