No one knows for certain whether Alexander the Great was poisoned at all, let alone by whom. His death in Babylon in 323 BC, at age 32, has been debated for over two thousand years, and the leading theories split into two camps: assassination by political rivals and death from natural disease. Both have credible evidence behind them, and neither has been definitively proven.
The Prime Suspect: Antipater
If Alexander was murdered, the most commonly named conspirator is Antipater, the regent he left in charge of Macedonia while he conquered the East. Antipater had good reason to fear for his life. Alexander had been removing and executing officials who displeased him after returning from India, and Antipater had spent years consolidating his own power back home. That kind of independence made people dangerous in Alexander’s eyes.
The ancient poisoning narrative goes like this: Antipater enlisted the help of Aristotle, who had his own reasons to worry after his nephew Callisthenes was implicated in an earlier assassination plot against Alexander. The poison was supposedly so potent it had to be transported to Babylon in the hoof of a mule. Antipater’s son, Cassander, carried it to the royal court, where it was slipped to Alexander by his cup-bearer, Iolaus, at a banquet hosted by a companion named Medius.
This account comes from an ancient text known as the “Liber de Morte,” a source many historians view skeptically because it may have been propaganda written after Alexander’s death to discredit political rivals. Still, the political conditions made assassination plausible. Alexander had alienated much of his inner circle by adopting Persian dress and customs, claiming to be the son of a god (an insult to the memory of his father Philip), and planning yet another grueling military campaign around the Arabian Peninsula and along the North African coast. His exhausted army had little appetite for more conquest, and he was surrounded by ambitious generals, each eager for his own share of the empire.
What His Final Illness Looked Like
Alexander fell ill after the banquet and deteriorated over roughly 11 days. The progression, recorded in what are called the Royal Diaries, went like this: it started with acute abdominal pain and fever, followed by worsening febrile episodes that fluctuated but trended upward. He then developed difficulty speaking, delirium, and a progressive paralysis that appears to have moved upward through his body. He reportedly remained mentally aware until very near the end, when he slipped into a coma and died.
One of the strangest details from ancient accounts is what happened after death. His body reportedly showed no signs of decomposition for six full days. To the Greeks, this was proof of what Alexander himself believed: that he was divine. Modern researchers have a very different explanation.
The Case for White Hellebore
Researchers who take the poisoning theory seriously have worked through the list of toxins that were available in the ancient world and could produce an illness lasting nearly two weeks. Arsenic and strychnine don’t fit the timeline or symptoms well. The strongest candidate is a plant called white hellebore (Veratrum album), which was well known in the ancient Mediterranean as both a medicine and a poison.
White hellebore poisoning begins with sudden pain in the upper abdomen and chest, often accompanied by nausea and vomiting. It then causes a dangerous drop in heart rate and blood pressure, along with severe muscle weakness. These features align closely with what the ancient sources describe over the course of Alexander’s decline. A 2014 toxicology review published in Clinical Toxicology concluded that if Alexander was poisoned, white hellebore offers a far more plausible explanation than any other known substance from the period.
The Case for Natural Disease
Most historians and medical researchers lean toward natural causes. Ancient Babylon was a hotbed of infectious disease, and the two leading candidates are typhoid fever and malaria. A detailed comparison of the Royal Diaries account with known disease patterns found that the symptoms, particularly the prolonged fluctuating fever over 11 days, are most characteristic of typhoid fever. Malaria remains possible but fits less neatly.
Alexander’s health was already compromised before that final illness. He had sustained numerous battle wounds throughout his campaigns, including a near-fatal arrow wound to the chest in India. He was also drinking heavily in the weeks before his death. A weakened, heavily scarred 32-year-old in a mosquito-rich river environment would have been highly vulnerable to waterborne and insect-borne infections.
The “False Death” Theory
In 2019, Dr. Katherine Hall, a clinician at the University of Otago in New Zealand, proposed a theory that reframed the entire question. She argued that Alexander contracted Guillain-Barré syndrome, an autoimmune condition in which the body’s immune system attacks its own nerves, likely triggered by an infection with Campylobacter, a common bacterium at the time. The specific variant she proposed causes ascending paralysis, meaning it moves upward from the legs, while leaving the mind intact. This matches the ancient descriptions of Alexander remaining mentally aware even as his body shut down.
Hall’s most striking claim addresses the six days without decomposition. She argues Alexander wasn’t actually dead during that period. As the paralysis progressed and his body’s oxygen demands dropped, his breathing would have become nearly undetectable. Ancient doctors determined death by checking for breath, not a pulse. Hall believes Alexander was falsely declared dead while still alive, making his case potentially the most famous instance of “pseudothanatos,” or false diagnosis of death, ever recorded. If she’s right, his actual death came days later than history has recorded.
Why the Mystery Endures
The honest answer to “who poisoned Alexander the Great” is that we may never know if anyone did. The political motive was real: Antipater, Cassander, and others had both opportunity and reason. The poison theory has a plausible weapon in white hellebore. But the natural disease explanations, whether typhoid fever or Guillain-Barré syndrome, fit the recorded symptoms at least as well and don’t require a conspiracy.
Part of the difficulty is that the ancient sources themselves disagree. The Royal Diaries, considered the more reliable account, describe what reads like a straightforward infectious illness with no mention of foul play. The poisoning narrative comes from later, more politically charged texts. And with no body to examine (Alexander’s remains have never been found despite centuries of searching), there is no physical evidence to settle the debate. What we’re left with is a 2,300-year-old medical mystery where every theory explains some of the evidence but none explains all of it.