Ah...here we go. As usual it seems like there has been some flipflopping on this issue. In 1964, the WT appeared to say it was okay for a doctor to transfuse someone who wasn't a JW, but it doesn't seem to be accepted later:
w64 11/15 682-3 Employment and Your Conscience
Christians in the medical profession are individually responsible for employment decisions. They must bear the consequences of decisions made, in keeping with the principle at Galatians 6:5. Some doctors who are Jehovah's witnesses have administered blood transfusions to persons of the world upon request. However, they do not do so in the case of one of Jehovah's dedicated witnesses. In harmony with Deuteronomy 14:21, the administering of blood upon request to worldly persons is left to the Christian doctor's own conscience. This is similar to the situation facing a Christian butcher or grocer who must decide whether he can conscientiously sell blood sausage to a worldly person.
*** w75 4/1 215-6 Are You Guided by a Sensitive Christian Conscience? ***
This Christian gave careful thought to the matter. It could be seen that it would not be right for a Christian to work exclusively for a blood bank, where everything was devoted to an end that was in violation of God's law. But that was not his situation; he ran tests of many kinds. Also, if one were a doctor responsible for the decision, one could not order a blood transfusion for a patient, any more than a Christian store owner could order and stock idols or cigarettes. However, this technician realized that in connection with blood he was merely running a test, even as a nurse might have taken the sample, a messenger might have delivered it to the laboratory and someone else might administer a transfusion or other medication on a doctor's orders. He reflected on the principle at Deuteronomy 14:21. According to that text a Jew finding a carcass of an animal that died of itself could clear it away by selling it to a foreigner who was not under the Law's restrictions about animal flesh not drained of its blood. So the technician's conscience at that time allowed him to run blood tests, including those of blood for transfusions to patients who did not care about God's law
*** w99 4/15 29 Questions From Readers ***
Some Christians working in hospitals have had to consider this factor of authority. A physician might have authority to order medications for or medical procedures on a patient. Even if a patient did not mind, how could a Christian doctor in authority order a blood transfusion or perform an abortion, knowing what the Bible says on such matters?