Congratulations on your pregnancy! Very exciting.
I would ask the doctor about why he/she wants the test taken so early. When I did the glucose tolerance test, my doctor allowed me to take the test using real, whole food instead of that yucky sugar solution. I had a bad reaction to that sugar drink the first time. I also had no history of GD and was of a healthy weight. Since my diet was really healthy to begin with, drinking that overly sugary drink really made me sick. I probably don't consume that much sugar in a week. Anyway, if you email me directly at ____@____.com, I can scan and email a copy of what he had me eat to run the glucose tolerance test. It might be worth running it by your doctor. It was a much nicer way to take the test. Also, go with your gut on this, unless there is a real risk to you or baby, postpone the exam until you are comfortable.
Best wishes! -J.