What kind of diabetes? It depends on whom you ask. My doctor says I'm not pre-diabetic. I say I am.
His proof is in looking at my HbA1c level on the last set of blood tests. I am not above the high end of the range, therefore I am not pre-diabetic.
My proof is in the guidelines given by various established diabetic associations. My proof also comes in how much (much!) better I feel when I do not eat highly refined grains and desserts. I have not consistently had any soda (pop) or other sweet beverages for several years. When I eat/drink these things, I have strong symptoms that are the same as diabetes.