Mixing of blood creates a very powerful bond and an exchange of psychological content. The donor and the recipient becomes connected not just physically but psychically. Therefore, it is a very serious connection with deep implications. If you are attempting to free yourself of psychological conditioning (defects, vices, errors, karma) yet donate blood to unknown persons, you are then adopting psychic principles from the recipients of your blood, thereby loading yourself with even more work to do.

Nevertheless, there are cases in which giving blood is the right thing to do.

The simple answer is: you can do what you will, just be aware that there are consequences for every action. It is good to be aware of the consequences before one acts.