One unit of platelets is equivalent to 800 ml of whole blood. if you want to donate one unit of platelets, you are not donating 800 ml of whole blood, because if you donate platelets alone, after you donate platelets, all the other components of blood will be transfused back into your body. If you want to donate platelets, you should pay attention to rest and do not eat fatty food or beans. It is recommended to rest for 1-3 days after the blood is drawn, avoid straining, avoid catching a cold and strengthen nutrition. You can consult your local blood center for specific matters, and generally the local blood center will have detailed instructions.