Hey there,
I just turned sixteen, and I'm going to be giving blood for the first time this week. I am not a vegetarian, but I don't eat any meat other than chicken and fish. I just want to make sure that I have high enough levels of what not in my blood so I am not rejected as a donor now that I have decided to neglect my fear of others stabbing me with a giant needle (cringe) and give blood

Is there anything I should be eating/not eating?
Thank you!