If the engine is not running, and it has been sitting a bit, it will read high, the fluid in the lines drains back to the pan while sitting( and some of the fluid in the torque converter depending on it's condition) wait until you start it up and put it into reverse , move a few feet, then drive, a few feet( this will bleed off most of the air in the system from sitting) then back to park ( set the parking brake)and check the leval while the engine is running.

If it's still reading high at this point then you may have a problem.( of course if your radiator is already starting to leak , it's replacement time for it anyway)