They have MISINTERPRETED Scriptures in Genesis 9:4; Leviticus 17:10; Deuteronomy 12:23; done under the "FIRST COVENANT" and Acts 15:28, 29 speaking of blood of animals for sacrifices.
We are currently under the "NEW COVENANT" and JESUS SAID in
Acts 10:13-15 says
"And there came a voice to him Rise, Peter; kill and eat."
But Peter said, Not so, Lord; for I have never eaten any thing that is common or unclean.
And the voice spake unto him again the second time, What GOD hath cleanses that call not thou common"
So we can eat anything we like as long as we bless it (Colossian 2:16).
I don't know where the GB got blood transfusions are not permitted in Scripture because in the OT "the blood" of animals for sacrifice were not permitted to eat in Genesis 9:4; Leviticus 17:10; Deuteronomy 12:23.
In Acts 15:28-29 it continues to speak of the blood of idols for sacrifice when it says
"For it seemed good to the Holy Ghost, and to us, to lay upon you no greater burden than these necessary things;
That ye abstain from meats offered to idols, and from [the] blood [offered to idols], and from strangled things [offered to idols], and from fornication [Not sexual but offerings to idols which are not Spiritual offerings to GOD]: from which if ye keep yourselves; ye shall do well. Fare ye well."
Now how they got "blood transfusions are not permissable" out of Scriptures speaking of "fornation" [Worshiping idols by offering the blood of animals as sacrifice] out of that
I DON'T KNOW!
It's no telling how many of their family members have died based on MISINTERPRETATION of Scripture!
It's just that IMPORTANT for people who MISINTERPRET Scripture and be in the WRONG doctrine worshiping the WRONG Jesus and will die [spiritually]
THE SAME WAY in a TWO baptisms belief (Ephesians 4:5) and setting up of "tables" as they did under the "FIRST COVENANT" (Hebrews 9:1-2)!
It reminds me of Scripture in the OT where they even burned their children in offerings to their god in Deuteronomy 12:31 which says
"Thou shalt not do so unto the LORD thy God: for every abomination to the LORD, which he hateth, have they done unto their gods; for even their sons and their daughters they have burnt in the fire to their gods."