Question: what do you have to do before donating blood?
Answer: Eat. Eating regularly before donating will help to keep your blood sugar levels stable. ... 
Drink. Almost half of the blood that you donate is made up of water. ... 
Exercise. Avoid doing any vigorous exercise or heavy lifting the day of your donation – both before and after you've given blood. ... 
Wear. ... 
Distract. ... 
Know.