120 minutes depending on the donor's health condition. Platelet donation After a short physical examination, the donor is taken into the donation room and sits in a chair next to the machine. The technician cleans one or both arms with iodine, or other disinfectant, and inserts the catheter into a vein in the arm. With some procedures both arms are used, one to draw blood and the other to return it. The process takes about one to two hours while blood is pulled into the machine, mixed with an anticoagulant such as sodium citrate, spun around, and returned to the donor. "Double needle" procedures using both arms tend to be shorter since the blood is drawn and returned through different catheters; with "single needle" procedures a set volume is drawn and processed in the first part of the cycle and returned in the second part. The donor's blood undergoes repeated cycles of draw and return. Side effects of the donation of platelets generally fall into three categories: blood pressure changes, problems with vein access, and effects of the anticoagulant on the donor's calcium level. Blood pressure changes can sometimes cause nausea, fatigue, and dizziness. Venous access problems can cause bruising, referred to as a hematoma. While donating, a supply of calcium antacid tablets is usually kept close by to replenish the calcium lost. Because the anticoagulant works by binding to the calcium in the blood, a donor's levels of calcium – and especially of active calcium ions – drop during the donation process. The lips may begin to tingle or there may be a metallic taste; since calcium enables the function of the nervous system, nerve-ending-dense areas (such as the lips) are susceptible, at least during the donation process. Unusually low calcium can cause more serious problems such as fainting, nerve irritation and short-duration tetany. Such an acute hypocalcaemia is usually due to low calcium levels prior to donation, aggravated by the anticoagulant. Hypocalcaemia can be curtailed by modestly increasing dietary calcium intake in the days prior to donation. Serious problems are extremely rare, but apheresis donors are typically not allowed to sleep during the long donation process so that they can be monitored. Aside from the procedure, donating platelets is different from donating blood in a few ways. Firstly, the donor must not take aspirin or other anti-platelet medications such as clopidogrel (Plavix) for anywhere from 36 to 72