To the original poster, like others have said, a healthy diet does not protect against GD, it is entirely hormonal. There isn't anything you can do to avoid it and sometimes the healthiest people can develop it. The test is only a few hours, and you're able to do it first thing in the morning so it's almost like you've slept in and pushed breakfast back by a bit. The fasting and specific level in the drink (like others have said, it's not really that massive an amount) is there so they can see just how your body reacts to a known quantity of sugars. At the end of the day, yes it is your choice whether you have the test or not but it is definitely something to really talk through with your healthcare provider so you truly understand what the test involves/the impact that GD can have on your child etc so you can make an informed decision.
I'm sorry SouthCoastChick, but as a GD mother I have to strongly disagree with your post and the dismissive way you are towards your diagnosis and the after affects. Just because you were fortunate enough not to experience negative effects does not mean that it is 'over dramatised'. You were under treatment, it may not have been completely effective treatment and you may have still been having issues with your sugar levels etc but have you considered that those sugar levels were WITH treatment and that without it they would have been significantly higher with the matching issue of probable complications for your child? Yes, you had the hassle of going to a bigger hospital etc but that is because smaller hospitals are not equipped to cope with complications IF they occur.
I'm sorry, but I would rather put up with the inconvenience of the tests, doing the finger prick test each day, injecting insulin (and I have a fear of needles so every finger prick and injection caused my anxiety to spike), travel to a different hospital and not need all of these precautions than dismiss them as 'unnecessary' and an inconvenience. Are they inconvenient ... yes, but at the end of the day my convenience wasn't my priority, the health of my unborn children was so I dealt with the inconvenience and anxiety. My 1st child was 8lbs, 2nd 6lbs 11oz and 3rd 7lbs 3.5oz, I had GD with all of them which was relatively well managed (insulin required for baby #3). Even with relatively good management, both my 2nd and 3rd children did experience mild complications, boardering on more serious complications for my 3rd. Their blood sugars were significantly lower than they should have been and both needed supplementation to get their levels up, my 3rd was borderline requiring special care nursery because of her levels and that was with my GD being controlled and levels in the 'acceptible' range for the most part with assistance from insulin injections. For my 3rd child in particular it was 2 days of heel prick tests every few hours making sure that her levels were back where they should have been, my others had the heel prick tests too but not for as long because their levels weren't as low/came up to 'acceptible' levels much faster.
OP, can you refuse the test, yes absolutely, but please use your midwife/doctor as the source of your information when making that decision, not people on an open forum like this one.