Leukapheresis is relatively painless, although it may cause discomfort, redness, and bruising at the venipuncture (vein puncture) site. Apheresis is common and regularly used for plasma and platelet donations. Donors may feel cold during the procedure, so blankets are provided to make sure you are comfortable. Fainting, although rare, may also occur. An abnormal drop in blood calcium may cause muscle spasms or numbness and tingling in the hands and feet. HemaCenter can provide calcium to help prevent this effect.