There seems to be a lot of misconception about people overdosing on kratom. Basically, it’s essentially impossible to actually overdose on the powdered leaf. The leaves contain a variety of alkaloids, 2 of which are primarily responsible for the plant’s opiate like effects, mitragynine and 7-hydroxymitragynine.
But the plant also contains what are believed to be opiate antagonists that become dominant over mitragynine and 7-hydroxymitragynine as dosage increases. This results in nausea, vomiting and general unpleasantness. It’s almost impossible to consume more than 1 ounce of powdered leaf at a time before these negative side effects makes it undesirable to consume more.
At the one ounce level, the amount of mitragynine and 7-hydroxymitragynine present is not anywhere near enough to cause an overdose even for someone with absolutely no tolerance. In a sense, it’s a built in safety mechanism.
Some, but not all, extracts remove the opiate antagonists, allowing for more to be consumed without the negative side effects becoming overwhelming. But with these, as dosage increases the effects level off, such that past a certain point there are diminishing returns where consuming more doesn’t really have any effect. Furthermore, to consume enough to actually get near an overdose level, it would be cost prohibitive.