Here's a portion of the Jensen letters as quoted by Marvin Shilmer:
"In conversation it was stated to me that it is a personal conscience matter whether a Christian decides to donate blood that will be used in fractionated forms, the same fractionated forms that we likewise leave to personal conscience as to acceptance. I was told this act being left up to each Christian's conscience naturally follows from what we have already published about decisions to accept fractions of blood." Letter dated 6/9/2001 page 4.
The Jensen Letters is the name given to a series of letters between an elder in the United States and the Watchtower Society, over the period 1998 to 2003... http://www.jwtruth.com/articles/BloodJensenLetters.aspx