Review: Kratom Toxicology and Risk Assessment Shows Few Hazards with Typical Use

Why it matters

A comprehensive peer-reviewed toxicology review concludes that traditional kratom consumption presents few health risks in non-polysubstance users, contrasting with FDA and state-level warnings and informing the risk-benefit debate.

The big picture

This critical literature review by Heywood, Smallets, and Paustenbach synthesizes ~200 peer-reviewed studies on kratom's pharmacology, toxicology, and epidemiology. The authors note confounding factors in kratom-related deaths (high co-use of opioids, alcohol, other drugs) and find that at traditional doses (2–20 mg/kg body weight), kratom is not expected to cause adverse health effects. The review identifies gaps in human dose-response research and calls for improved product quality control.

Key findings

• Traditional kratom consumption via tea or powder at typical doses not expected to cause adverse health effects in humans; Mitragynine comprises 2% of dry leaf weight, 7-OH comprises <0.02%, with significant product variation; Deaths attributed to kratom frequently involved multiple confounding substances with unclear direct causality; Product quality control inadequate; alkaloid concentrations vary 3–60x across commercial powders and capsules; Kratom may have therapeutic potential in some persons with few risks from non-polysubstance use

What they say

Traditional kratom consumption via teas or chewing of dry leaves, where mitragynine concentrations are generally <15–30 mg/g and doses often <2–20 mg/kg-bw/day, is not expected to yield adverse health effects in human users.

Bottom line

Evidence suggests traditional kratom products pose minimal health risks at typical doses in isolation, but synthetic derivatives and polysubstance use elevate risks significantly.