Hi Catarina, you have to check with the donation center for a complete
assessment on your eligibility for donation. I have included the American
Red Cross criteria below. Medication does not automatically exclude you from
donating in most cases but it is dependent on you, the condition, that would
be the limiting factor. They don't want anything to happen to you when you
donate. The medications that would exclude are those associated with blood
clotting interference or biohazard substances.
The red cells are separated from the plasma and the white cells and
suspended in citrated saline.

http://www.redcross.org/services/biomed/0,1082,0_557_,00.html