Mean platelet volume is the size of the platelets. The higher the MPV the larger the platelet size and the lower the MPV the smaller the platelets. High MPV can cause a person to be at a higher risk for strokes and heart attacks. Low MPV can cause a person to be at risk for bleeding problems (too much bleeding that is slow to stop). There are some natural anti coagulants that help lower MPV blood like flax seed oil and fish oil.