Plasma is the cell-free part of blood that helps maintain our circulatory volume and supplies proteins needed for blood clotting and immunity. Donated plasma usually is used to control bleeding, often among burn victims and newborn babies in critical condition. It is also given to patients with leukemia, those who have had organ transplants, as well as to some in treatment for heart disease.
Donating plasma is a bit more time-consuming than giving whole blood: the plasma itself is removed from whole blood via a separation process called plasma apheresis. Here's the way it works: after blood is drawn in the usual way via a needle placed in your arm, it goes into a centrifuge that separates out the plasma. Concentrated blood cells and platelets are then returned to your body. The procedure takes about 15 to 20 minutes longer than a regular blood donation.
Your body replenishes any plasma you donate in 48 hours so it is considered safe to give more as soon as two days after a first donation. However, the American Red Cross limits plasma donations to 12 a year, so you're better off donating once a month rather than once a week. Some blood centers impose longer waiting times between donations.
Anyone eligible to donate whole blood is eligible to donate plasma. The Red Cross requires all donors to be healthy, at least 17 years old, and weigh at least 110 pounds. If you have a chronic disease, you're considered eligible to give blood as long as you're being treated and you feel well. If you've been taking certain medications, you may be asked to wait a while before becoming a donor.
If you or someone you know has been donating plasma or whole blood, I applaud you. Although there is an urgent need for blood, only five percent of Americans donate in any given year. Giving blood is safe, it is easy and, as the Red Cross says, it is the right thing to do. (Incidentally, because it lowers iron levels, it may also be the healthy thing to do. Lower iron correlates with lower risks of both heart disease and cancer.)
Andrew Weil, M.D.