Tasigna : dosage gap 11.30 hrs

I very much doubt that feeling tired has anything to do with when you are taking your dose (especially half an hour from recommended time).  I try as much as possible to take them 12 hours apart, but sometimes it is 10 hours, 8 hours, 13 hours, etc.  I am not doc but I believe the important thing is to not miss any doses and take them on opposite sides of your day (12 hours whenever possible), oh yeah and fast before and after.  Feeling tired from time to time is normal and could possibly something missing in your diet.  I remember going through a couple of bouts where I felt like I could go to sleep while driving if I didn't roll my window down and shake my leg, etc.  Most days I feel totally normal.