on my testing kit it shows a heap of places on the body you can take the test. And its says the shown pictures are generally the least sensitive. I always assumed blood is blood.
I failed both tests, but was more borderline if anything. The dietician explained to me they would rather treat you as if you are diabetic because otherwise it could be worse for the baby.

I controlled mine through diet, i think it was the best thing for my pregnancy. I didnt put on barely any extra weight and i felt great for a lot longer. To me, even though i was in no mans land as far as blood sugar, treating it as worst case was better for me.