See my sibling comment - you almost certainly can overdose on it; one of the papers I linked had them deal with comatose patients and blood cloths. But it takes absolutely stupidly high doses, and even then all of them left hospital within 48 hours.

Both the papers I linked involved snorting large amounts of LSD in powder form thinking it was cocaine, rather than eating a tab, and these two papers are the only examples I know of reporting that, almost 50 years apart, and with no deaths.