Not to worry! MPV (mean platelet volume) on a CBC (complete blood count) is one of the indicators of platelet size. The "normal" range of 9.8-12.7 is where most people will fall, but numbers slightly out of that range (like yours of 13.8) are for the most part in the normal spectrum. These numbers can vary from test to test and day to day with hydration status, normal variability in the lab results themselves, etc. I would not do anything and would not worry about this unless there were other indications that you had platelet dysfunction (abnormal bleeding, low platelet count, low blood counts, etc). This is a common issue that arises when patients get the lab reports that show a "L" or "H" highlighted by the computers next to results that are actually not concerning and normal findings. Hope that provides some reassurance.