jesus said it was ok to heal a man on the sabbath, breaking a direct law from god about “ working” on that day. - Morph
Jesus was meticulous about keeping the Law and taught his disciples that they must do likewise. He disagreed with the Pharisees on the interpretation of the Law.
The law on blood was more than a dietary restriction it was about respect for life. Since no life is surrendered in the donation of blood then transfusions do not contravene the law.