How low should my blood sugar be when I have gestational diabetes, and how does my doctor make this diagnosis?
The protocol I use in my practice is if the O'Sullivan (glucola screen) test is abnormal at 24 to 26 weeks, I then move up to the three-hour glucose tolerance test. If two out of the four blood samples are abnormal, that's when I make the diagnosis of gestational diabetes.
If your doctor labeled you as gestational diabetic on the glucola screen alone, he or she may be using this technique to justify an ADA diet (American Diabetes Association). It's jumping the gun, but there's no real harm here, especially if you're continuing to test your sugars. Even if you were on such a diet and not even diabetic, it's a nice diet for any pregnant woman, because it avoids inappropriate weight gain.
If foregoing the full glucose tolerance test was a mistake, you'll see evidence of this on the blood sugars you've been taking. (Perhaps your doctor was being sensitive in not putting you through a major pain-in-the-behind test.)
How low is too low? A sugar level so low that you're dizzy, pass out, or become ill is too low. If there are no deleterious effects, a low blood sugar is not harmful to you or your baby. (The baby takes all of the sugar it can and leaves the rest for you.)