The cause of Poes death remains unknown. He was found unconscious on the street in Baltimore, and taken to a hospital, where he died several days later without ever regaining consciousness. The mystery of Poes death has produced a lot of discussion over the years. Various authors have suggested a variety of possible causes for his death including delirium tremens, heart disease, epilepsy, syphilis, meningeal inflammation, cholera, and rabies. None of the speculations has been generally accepted, apparently because none explains the full set of observations. But it seems to me the real answer may be much simpler.
One key to the answer is to remember that a number of people have noted Poes reputation as a drunkard. He was known to drink occasionally or frequently, depending on whose description is used and was often seen in an inebriated condition. In fact, his drinking was the reason that his name was crossed out of the family Bible. But there was another piece to Poes reputation as well: He was known to have a very low tolerance for alcohol, and it was said of him that one glass of wine would put him under the table. This very low alcohol tolerance is characteristic of an individual with diabetes.
The other key comes from family history. At least parts of the Miller, Daffron, and Poe families were quite close. Elements of these three families traveled down the Ohio River together, settled in southeast Missouri, and intermarried over multiple generations. (These are collateral lines, not descendants; Edgar Allan Poe had no children.) And it is notable that diabetes is quite frequent among these families in the 20th century, generation after generation.
The prior observations and this history suggest the possibility that Edgar Allan Poe was diabetic. (Diabetes could not be readily diagnosed or treated during Poes lifetime.) If so, he may have passed out in Baltimore due to low blood sugar, and not due to being drunk as has so long been asserted. And if that is the case, it adds to the tragedy of his early death as it raises the likelihood that he could have been revived at any time during those last days in the hospital by simply pouring some fruit juice in his mouth.
This description is not definitive. It is certainly possible the diabetic tendencies enterred these family lines from another direction and/or at a later time. Nevertheless, the combination of the family history of diabetes and the historical observations of Edgar Allan Poe is very suggestive. And this suggestion does explain the observations during Poes lifetime and at the time of his death.