Jesus came to fulfill the Law.
Do Catholics really seriously believe that Jesus would have commanded His disciples to drink blood in violation fo the Law He came to fulfill?
How was He to remain the spotless Lamb of God in that case when He commanded someone to do something sinful, that would make them unclean?
He fulfilled the law, and at the same time he did away with laws that were no longer beneficial.
Christians don’t follow that old Jewish law that one can’t drink blood - because Christ did away with it when he became the Passover Lamb.