One can donate blood every 4 to six months not every three months. It takes about 120 days or four months for the body to create fresh blood in place of donated blood. Also, the quantity of blood in ones body varies from person to person but generally it is considered to be about one eighth or one tenth of the total body weight. So if someone's weight is, let's say, 80 KG then that person will have approximately 8 to 10 liters of blood in his her body.

The following is some more informative detail about blood groups:

Blood Group Information





Does Your Blood Type Reveal Your Personality?

According to a Japanese institute that does research on blood types, there are certain personality traits that seem to match up with certain blood types. How do you rate?