http://revach.net/article.php?id=3925

Section: Halacha   Category: Daily Halacha
Rav Shlomo Zalman Auerbach & Rav Elyashiv: Washing Netilas Yadayim After A Blood Test

The Shulchan Aruch (OC 4:19) says that after bloodletting from your shoulder, if you don't wash Netilas Yadayim you will be scared for seven days.  What if you donate blood, or you take a blood test, or if you cut yourself and bleed, must you wash Netilas Yadayim?

The Nishmas Avrohom brings that some say since this is a Din from the gemara, it is worthwhile to be machmir even when you give blood for lab tests.  If so he says then why not also wash when you get a cut?  He brings from Rav Shlomo Zalman Auerbach that you only need to wash after you let blood for the sake of curing yourself from excess blood.  He holds that since this is segula, we need not take it further than the actual words of the gemara.  When asked regarding giving blood for the health of others, Rav Shlomo Zalman answered that you only need to wash when done for your own refuah.  Since giving to others is a mitzva, nothing bad will happen from it.

In a tshuva from Rav Elyashiv, writes the Nishmas Avrohom, he says that giving blood is included in what the gemara says about bloodletting and you should wash your hands as per the Shulchan Aruch.  However even Rav Elyashiv agrees that after giving blood for a lab test you need not wash your hands.

Important Note: We try to convey the Tshuva to the best of our ability. We admit that our understanding may not be accurate. One should learn the tshuva to verify the accuracy of our interpretation.  Please also understand that this Tshuva may not be the final word on this topic. One should consult a Rav before drawing any conclusions.