I Have An Employee Who Has All Of The Sudden

I have an employee who has all of the sudden become shaky and had weird speech as well as balance was off when walking. He claims this has only happened the 2 times. and he isn't diabetic. When this has happened he waited it out for about 30 minutes to an hour and it seems to go away. I am worried about this. is it drug use or can this be a medical condition.? sorry not paying for this. forget it