Those tests make no sense to me. They test your ability to handle sugar intake - so what if you don't eat sugar!?
Ask for a fasting insulin test, maybe an A1C. Definitely stick to Primal. Do not do the sugar-drink. I have heard they will sometimes allow a person to do a meal test if the grams of carbs are the same.
Ask about your options. Primal is so healthy. Yuck on that darn GTT. So outdated. Just avoid the glucose and you should be fine.