When you've worked in the medical field long enough to know they should have carried his ass to a hospital after being injected with a needle that had probably been used already
But yaoi logic
When you have a fear of needles and was uncomfortable the whole time reading the manga ;-;
They took the liberty to inject him with a different needle instead ٩(๑❛ᴗ❛๑)۶
When you've worked in the medical field long enough to know they should have carried his ass to a hospital after being injected with a needle that had probably been used already