It's admirable to want to donate blood. I commend you as that is very important. Use of pot doesn't harm the recipient of your blood product. However, most blood banks will not accept blood from someone they suspect has used marijuana recently or had alcohol recently. Not sure how they can tell but know someone turned away. As to privacy. I'm sure they wouldn't share that with your employer. Privacy laws prevail. However, again, they could test the blood and not use it or accept you. Hope you have had a diagnosis by now for your condition and are feeling better. Best