I worked at a plasma center and I can you tell you they don't check for drugs. Just HIV, HEP B and C, and at our place Syphillis also. The only thing is you have to make sure not to smoke before you donate because it can raise your pulse and blood pressure and those have to fall within certain guidelines. Also you can make a hell of alot more money donating plasma. With blood you can only donate every 56 days-that's how long it takes to regenerate RBC's. But with plasma you can donate twice a week as long as you eat right and are always well hydrated.