Two claims circulate about this, and both are wrong.

One is that kratom has killed a hundred people and is a public health menace. The other, common among sellers and enthusiasts, is that you cannot overdose on it at all. The data supports neither. It supports something more specific and more useful.

The numbers

The most systematic analysis available comes from the CDC, examining overdose deaths across 27 states between July 2016 and December 2017.

  • 27,338 overdose deaths were recorded in the dataset
  • 152 tested positive for kratom, which is 0.56%
  • Kratom was determined to be a cause of death in 91 of those
  • Of those 91, only seven had kratom as the only substance detected among those tested for
  • Fentanyl was present in approximately 65% of the kratom-positive deaths
  • Heroin was present in roughly one third

Reading it honestly, in both directions

Against the alarmist reading: kratom appeared in about one in 180 overdose deaths, and in the overwhelming majority of those it was one substance among several in people who were also using fentanyl or heroin. Seven deaths across an 18-month, 27-state dataset with kratom as the sole detected substance is a genuinely small number, and it is inconsistent with describing kratom as a major driver of overdose mortality.

Against the "you cannot overdose" reading: seven is not zero. People have died with kratom as the only substance detected. Any claim that fatal outcome is impossible is contradicted by the record, and anyone making it is either uninformed or selling something.

One caveat that cuts both ways: toxicology only finds what it tests for. "Only substance detected" is not the same as "only substance taken."

Why fatal outcomes alone appear to be rare

The pharmacology gives a plausible explanation. Mitragynine is a partial agonist at the mu-opioid receptor with relatively low intrinsic efficacy. Partial agonists produce a ceiling effect: past a certain point, more drug does not produce proportionally more receptor activation. Buprenorphine, an approved medication, works on the same principle and its respiratory safety profile reflects it.

This is a real mechanistic difference from full agonists such as morphine, oxycodone and fentanyl, which do not have that ceiling and where escalating dose escalates respiratory depression without limit.

A note on how this is often explained: you will frequently see kratom's profile attributed to "biased agonism," meaning selective activation of G-protein signalling over beta-arrestin recruitment. That hypothesis has been substantially challenged since around 2020, when research found that beta-arrestin-2 knockout mice still experienced opioid-induced respiratory depression. Partial agonism is the better-supported explanation. The conclusion survives, but the popular version of the mechanism is out of date.

The circumstance that actually kills people

This is the practical point and the reason this article exists.

The ceiling effect protects against overwhelming the receptor with kratom. It does not protect against additive respiratory depression from something else acting on the same system. Combine kratom with a full opioid agonist, a benzodiazepine, or alcohol, and the depressant effects stack.

That is what the mortality data describes. Fentanyl in roughly two-thirds of cases. Heroin in a third. This is not a coincidental finding, it is the mechanism of nearly every one of these deaths.

If there is one thing to take from the entire body of evidence on kratom safety, it is this: combination is the risk. Not the substance in isolation.

What this does not tell you

Mortality data measures deaths. It says nothing about non-fatal harm, liver injury, dependence, or interactions with prescription medication, all of which we cover separately and none of which appear in an overdose statistic.

"Rarely kills people directly" is a low bar and a narrow claim. It is not a safety profile.

Sources

This is information, not medical advice. If you believe someone is experiencing an overdose, call emergency services immediately. Verified Botanicals sells botanical material for reference and research purposes only. Not intended for human consumption.