Here is an excerpt from leavingwt DA letter found here at jwfacts.com
http://www.jwfacts.com/pdf/leavingwt-da-letter.pdf
The Bible is silent on the topic of blood transfusions. However, I am deeply interested in how God feels about the matter . The following illustration has been helpful to me: If you were robbed and a thief demanded your wedding ring, would you refuse to give it to him if he threatened to kill your spouse? Would you reason: "This ring represents my marriage to my spouse and that's more important than my spouse’s life"? Such reasoning is seriously flawed yet this is the exact reasoning used by Watchtower to support its ban on certain types of blood transfusions. Yes, blood is a symbol of life, but life itself is certainly more valuable than the symbol!
To me that pretty much nails it down to show how silly it is to refuse blood, the symbol, that would save the thing it is symbolizing.
NJY