Comment by lesuorac

There's kinda a significant difference between bloodletting and blood donation.

For starters, you're not supposed to donate blood when you're sick.

The other being the quantity. A donation is 1-2 pints. Wikipedia lists bloodletting as easily 3 pints [1].

[1]: https://en.wikipedia.org/wiki/Bloodletting#Use_in_the_1600s_...