But your doctor actually told you the following: 'abstain from alcohol before you drive'
In the same manner God directed the Israelite's to abstain from blood when they had killed an animal for sacrifice. The abstinence from blood was always in connection with the taking of a life. If an Israelite farmer found an animal "already dead" he was free to eat it with impunity. Lev. 11:38,39. Blood is not intrinsically sacred; it is only sacred insofar as it represents a life that has been taken.
The main purpose of a blood transfusion is to preserve life and has nothing to do with the taking of a life. Hence according to JW reasoning and usage of the 'blood is sacred' mantra, transfusions are perfectly ok according to the Hebrew god.