[Avodah] donating blood

[Michael Kopinsky]

On 3/17/07, Eli Turkel <eliturkel at gmail.com> wrote:
> Someone claimed that donating blood to the Red Cross is against halacha
> since one is "harming oneself" and most receipients are nonJewish.
> Seemed strange to me as most poskim allow even violating shabbat on behalf
> of a NonJew because of possible sinah. Why would donating blood be any
> differewnt?
> Any opinions (piskei halachot) ?

I find this difficult to accept:

a) How do you know if it's going for a goy?  Maybe a Jew will get it, and
safek pikuach nefesh is enough.  (Is this called safek pikuach nefesh?)

b) Meiheicha teisi that you're harming yourself?  I would like to know
what the medical journals saying about this.  (Not the Red Cross PR dept.)