Question: how long should i eat before donating blood?
Answer: In the days before your donation, eat healthy, iron-rich foods such as spinach, red meat, fish, poultry, beans, iron-fortified cereals and raisins. ... 
Get a good night's sleep.
At least 3 hours before donating, eat a balanced meal and avoid fatty foods, such as hamburgers, fries, or ice cream.
Drink an extra 16 oz.