Possible side effects of blood donation and how to prevent them

A blood spurt (bruise) in and around the site of the vein puncture.
The risk of this complication can be reduced immediately after the procedure by proper compressing the puncture site - do not bend the arm, later by administering cold compresses and applying ointment.
General reaction, fainting. They are caused by less than optimal adaptation of the donor's blood circulation to the resulting blood loss. Fainting occurs most often in starving, under-watered, tired and "rushed" donors. Adequate diet before donation, a sufficiently long stay at the donor bed and cooperation with the staff of the transfusion department are the preventive measures.
Don't be afraid to tell the medical staff that you feel weak after the donation, don't overestimate your strength.
It is advisable to alert the nurse in advance of any nausea or other discomfort associated with the donation.
Get out of the gurney slowly.