Definitely do the 3h glucose test. The thing about the 1h test is your system is bombarded with an abnormally large amount of sugar in a short time and the blood test will measure your response to it - this is quite different from measuring your levels throughout the day which may be more "normal" because your sugar intake could have been at a relatively low level. In essence, testing your levels throughout the day is not necessarily a good indicator of whether you have GD or not. That being said, it is not uncommon for a pregnant women to fail the 1h test but pass the 3 h test - usually, this is because fasting rules may not have been followed for the 1h as Kelly said.
Was the one hour fasting? When I did my one hour, it was not fasting, therefore if you ate anything high in carbs prior, your glucose level may have been high. With my last pregnancy (only made it to 9 weeks), they I failed my one hour with over 200, took the 3 hour and passed that...I think being it was fasting. (They have me test early b/c my Mom had Gest. Diabetes)......The blood test is generally more accurate than a regular glucometer.....I'm an RN and sometimes we play around and check our own on the hospital units and get different readings every time...one right after another,......