After eating blood glucose levels?

I ate pasta with ceasar dressing, chicken, and vegetables. I tested myself two hours later and my number was only 64. Isn't it supposed to be higher? Why is my sugar always so low. I know that this is pretty much the opposite of diabetes, which my grandma, grandpa, dad, and two of my first cousins have. My highest number lately has been 88 and my lowest 47. Can low sugar be a precursor to diabetes?