It's more funny, at first, that the young man isn't trying to escape his grip. No matter how overwhelming his bite could be, it was rarely the sort of thing that anyone wanted more of. So he drank long and deep, as sense came back to him little by little... it was just when the flow of blood began to slow and Karkat's pulse began to weaken that he realized that he should stop. It was a plain and simple academic realization that if he did not, this boy would die, and such things caused trouble.

Jacob withdrew his fangs, licked the puncture wounds closed, and held Karkat at arm's length. He wasn't dead, but in that state, in his experience, he wasn't likely to survive without immediate transfusion. "...well." Had he been a little less emotionally gutted, there might have been cursing. As it stood, all he could manage was dismay and some practical rolling up of his sleeve. A quick flash of fang and his wrist was torn open, and then he was pressing it to the young man's lips. Later there would be time to concoct excuses and formulate plans. Now, he'd have to hope that the lad could still swallow properly. Supporting Karkat's weight, he slowly knelt, ready to lay him out in the snow and give him some room and space for the changes to occur.