Is blood allowed to leave the body for Jehovah’s Witnesses ?

Sometime surgeons suggest to extract some of the patient’s blood a few weeks before the surgery. When needed it can then be used during the surgery. This is sometimes called an autotransfusion.
This has the advantage that it cannot be contaminated by another one’s diseases and doesn’t cause rejection symptoms
Still, this treatment is unacceptable to the Governing Body of Jehovah’s Witnesses. Why?

The Watchtower, 2000, Oct 15th, pages 30, 31: question from readers

However, such collecting, storing, and transfusing of blood directly contradicts what is said in Leviticus and Deuteronomy. Blood is not to be stored; it is to be poured out—returned to God, as it were.

The scripture in Leviticus is specifically about hunting (Lev 17:13)
The scripture in Deuteronomy is specifically about killing an animal for eating or as a sacrifice (Deut 12:15,16; 15:23)
When someone’s own blood is transfused, no animal or human is killed: hence there is no life to be given back to God
But even then: the laws of Moses are abolished
This is recognised in the above mentioned Watchtower. Yet, this law is somehow still considered in force, whereas other laws not (like stoning to death, that the hair on the side of the head could not be shaved, or the field cannot be reaped to the edge). No biblical reason is given.
On the other hand, some treatments that are similar are said to be a matter of conscience.
The Governing Body allows taking blood fractions. Yet they come from collecting, storing and then partially transfusing

Treatment	Extracted	Stored	Given back	Poured out	Acceptable ?
Autotransfusion	Yes	Yes	Yes	No	No
Blood work	Yes	Yes	No	possible	Yes
Blood tagging	Yee	Yes	Yes	No	Yes

_{Autotransfusion: extracting, storing and then returning your own blood during surgery. Blood work: extracting blood, storing it until it reaches a lab where it is examined; usually it is stored a while longer in case additional examinations are requested. Blood tagging: some blood is extracted. Then the blood is machined for a few hours; a substance is added which is easily seen on scanners in order to locate i.e. haemorrhages; during the processing the patient is usually allowed to walk around. Then this processed blood is given back to the patient after which the patient is scanned. More examples are to be found in Our Kingdom Ministry of November 2006, page 6}

Are all Bible laws still valid when a life is in danger ?

MAR 2:25, 26

Have you never read what David did when he was in need and he and the men with him were hungry? He entered into the house of God and ate the loaves of presentation, which it is not lawful for anybody to eat except the priests.

MAR 3:4; MAT 12:11, 12

Is it lawful on the Sabbath to save a life? If your only sheep falls into a pit on the Sabbath, is there a man among you who will not grab hold of it and lift it out? How much more valuable is a man than a sheep! So it is lawful to do a fine thing on the Sabbath.

What is more important: life, or its symbol: blood ?

MAT 23:16, 17

Woe to you, blind guides, who say: ‘If anyone swears by the temple, it is nothing; but if anyone swears by the gold of the temple, he is under obligation. Fools and blind ones! Which, in fact, is greater, the gold or the temple that has sanctified the gold?

LUKE 9:25

Really, what good will it do a man if he gains the whole world but loses his own self or suffers ruin?

Sometimes it was allowed to eat an animal with its blood still in it. This could help a hunter to stay alive if he didn’t catch anything else.

LEV 17:15

If anyone, whether a native or a foreigner, eats an animal found dead or one torn by a wild animal, he must then wash his garments and bathe in water and be unclean until the evening; then he will be clean.