Hi mandaa- don't worry too much about this. For the one hour, you typically need to score below 140 to pass. My doctor's office uses stricter standards and I needed to be below 130. I scored 140 on the dot and had to take the three hour.
For the 3 hour, they give you a higher concentrated sweet drink (like twice as much sugar as the one hour concoction). There are four "check points" you need to pass: <95 fasting, <180 1 hour, <155 2 hour, and <120 3 hour I believe. Most doctor's offices say you need to fail two steps for the dx. My doctor says if you fail one step, it's an automatic dx. I passed every step except scored a 190 at 1 hour which was enough for my OB to label me with GD. The test isn't too bad. The drink is nasty sweet, and I was really hungry by the end, but I didn't feel sick or nauseous or anything.
Honestly, of the issues I'm working with now, GD is the most manageable, least scary, and in some ways may even be a blessing in disguise. I went to the clinic and am now following the diet closely. It's a very healthy diet. My numbers have all been good so far with diet changes alone, and I've actually lost 2 pounds since starting it! It's truly not the worse thing that can happen... And you never know, you could pass the 3 hour and not have to worry about any of this anyway!