Trying out crossposting

At a blood drive:

NURSE (frowning at vein on my left arm): Show me your other arm.
ME: *does so*
NURSE: Oh, those are good! Yummy!
ME: *OMG vampires*
NURSE: You've given blood from the right arm before, right? See? *points*

I then notice a couple of little marks on the bend of my arm which, had I noticed them before, would have dismissed as freckles, insect bite scars or scratches.

So, that's what needle marks look like.