IMPORTANT QUESTION

I have to get up early to see my obgyn , but not for an appointment, they told me to show up for bloodwork . im not sure if its to check if i have diabetes or what but they told me at 12 am do not eat anything or drink anything until i come to see them in the morning. Im am soooo hungry right now and my stomach is literally talking to me. Do i really have to not eat anything ? Or can i get a snack , and do you think it would mess up anything that there trying to do?