Should I Fast?

So... I have my glucose test tomorrow and my dr and the appt line told me to eat something before I go but no carbs. Meaning no bread, cereal, yogurt, things like that. But now I'm being told by others I need to Fast 12 hours before my appt. I'm really bad with not having food in my system. I tend to get very shakey, pale, and weak. And if I wait too long I'll pass out. So what do I do? I called the advice nurse to get a 3rd opinion but if I don't get a call back do I fast or not fast?? This is frustrating. 😑