Context: Markus got poisoned taking a hit for his sister. Again. And The doctor taking care of him says he doesn't have much of a chance of survival.
M
ore context: Markus is alive and conscious thanks to his half elf blood. Which makes elves poison resistant. He isn't unaffected but his chance of survival is much higher because of that. He doesn't appear to be an elder to the doctor was unaware of this factor. Yay, but not really.