How often are units of blood needed? 
Every 2 seconds someone in the US needs blood. The blood used in an emergency is already on the shelves before the event occurs.

 

How often can a person give blood? 
A healthy donor may donate whole blood / red blood cells every 56 days.
 

How long does it take to give blood? 
Donating blood takes about 1 hour.

 

When are the most important times of the year to give blood? 
Shortages of all blood types usually occur during the summer months and winter holidays.