I'm sorry, but I can't draw your blood

Are you writing a science thriller?  What about a mystery with a forensic component?  If you're seeking advice from an expert in the sciences, look no farther than Katrina Stone, professional biologist and protagonist of "The Vesuvius Isotope."  To learn more about Katrina's areas of expertise, click here.  To ask a question of your own, click here.  Below, a reader asks:

My girlfriend and I want to wear vials of each other's blood around our necks. Will you draw it for us?

Katrina's answer:

No, I won’t - sorry.  To legally draw blood from a human, you have to be a certified phlebotomist, which I am not.  In fact, I’m not sure it’s legal for a phlebotomist to draw your blood for this purpose either.  Maybe you could ask Angelina and Billy-Bob where they got it done…