Hi ironhorse! I'm an MD..the level he was checking is called creatnine kinase(CK). This is an enzyme released by muscles when they are stressed or damaged. If you have muscle mass/percentage that is significantly greater than the average adult and have completed a strenous workout prior to going to your doctor, your CK will be slightly elevated. In the future, wait at least 24 hours after a workout before letting him check your bloodwork