What Wolfman85 and Cofty said.
To repeat:
The whole point of the scriptural prohibition is that the blood represents the soul or life that has been lost. The blood is a symbol only of the life lost.
There is not a single scripture where the prohibition is given where a soul has not been lost. In all cases, the blood not to be consumed has come from a dead soul.
Is any soul or life lost in the case of a blood transfusion?? None whatsoever.
With a blood transfusion the blood has absolutely no symbolic value as there is no loss of life.
Case closed.