Kratom doesn’t fit neatly into a single classification. Botanically, it’s a tropical tree in the coffee family. Pharmacologically, researchers describe it as an atypical opioid because its active compounds partially activate the same receptors as traditional opioids but behave differently in important ways. Legally, it occupies a gray zone: not a controlled substance under federal law, but not an approved drug or a standard dietary supplement either.
Botanical Classification
Kratom (Mitragyna speciosa) is a tree native to Thailand and neighboring Southeast Asian countries. It belongs to the Rubiaceae family, the same plant family that includes coffee. The leaves contain dozens of active compounds, but two get the most scientific attention: mitragynine, which makes up the bulk of the leaf’s alkaloid content, and 7-hydroxymitragynine, a more potent compound that the body also produces when it metabolizes mitragynine.
Why Researchers Call It an “Atypical” Opioid
Kratom’s two main compounds both activate mu-opioid receptors, the same receptors targeted by drugs like morphine and oxycodone. But the activation is partial and complex, which is why the label “atypical” keeps coming up in the scientific literature. The effects only partially compare to those of traditional opioids.
7-hydroxymitragynine is the more straightforward of the two. It binds to mu-opioid receptors with roughly nine times the affinity of mitragynine and acts as a partial activator, producing pain relief in animal studies. Mitragynine is more complicated. In isolated human receptor tests, it actually blocks the mu-opioid receptor rather than activating it. Yet in living animals, it behaves more like a weak opioid. The explanation appears to be that mitragynine also interacts with several non-opioid systems, including receptors involved in adrenaline signaling, serotonin, and dopamine. This mix of activity is likely why kratom users report both stimulant-like energy at lower doses and sedation at higher ones.
One distinction that drives much of the research interest: some evidence suggests kratom’s compounds may not suppress breathing the way traditional opioids do. Respiratory depression is the mechanism behind most fatal opioid overdoses, so the possibility that kratom activates opioid receptors without this effect has drawn attention from scientists studying alternatives for pain management and opioid withdrawal. That said, the way kratom compounds activate these receptors still raises concerns about addiction potential, even if the risk may be lower than with conventional opioids.
Federal Legal Status in the U.S.
Kratom is not a scheduled substance under the Controlled Substances Act. The DEA considered emergency-scheduling it in 2016 but withdrew the proposal after public backlash and requests from members of Congress. As of now, you can legally purchase kratom leaf products in most of the United States at the federal level.
The FDA, however, has taken a firm stance against it. The agency classifies kratom as a “new dietary ingredient” that lacks adequate evidence of safety. Under this designation, the FDA considers kratom-containing supplements to be adulterated, meaning they violate federal food and drug law. In practice, this means the FDA can block kratom imports at the border and has done so through a standing import alert authorizing the refusal of kratom shipments.
A newer development targets one compound specifically. In early 2025, the FDA recommended scheduling concentrated 7-hydroxymitragynine (often sold as “7-OH” products) under the Controlled Substances Act. The agency was careful to note this recommendation targets concentrated 7-OH products, not natural kratom leaf. The DEA is reviewing this recommendation and would need to complete a formal rulemaking process, including public comment, before any scheduling takes effect.
State-Level Laws Vary Widely
Several states have banned kratom outright, while others have passed what’s known as the Kratom Consumer Protection Act, a model law that keeps kratom legal but regulates it with age restrictions, labeling requirements, and limits on contaminants. The patchwork means legality depends entirely on where you live. Some states, counties, and cities have their own bans even where state law is silent. If you’re checking legality, look at your specific state and local laws rather than assuming federal status applies everywhere.
International Classification
Kratom is not controlled under any United Nations drug treaty. The World Health Organization reviewed kratom, mitragynine, and 7-hydroxymitragynine through its Expert Committee on Drug Dependence and confirmed that none are currently under international control. Individual countries set their own rules: kratom is illegal in Australia, several European nations, and, ironically, Thailand banned it for decades before re-legalizing it in 2021.
Safety Profile and Known Risks
CDC overdose surveillance data from 2024 identified kratom or mitragynine in 413 fatal drug overdoses across 43 reporting jurisdictions. That number needs context. The vast majority of those deaths involved other substances as well, particularly traditional opioids and stimulants. Deaths involving only kratom and no other drugs are rare, though they have been documented.
Regular kratom use can lead to dependence. People who use it daily and then stop often report withdrawal symptoms similar to, though generally milder than, opioid withdrawal: irritability, muscle aches, insomnia, and nausea. The compounds do activate opioid receptors, and the body adapts to that stimulation over time. Researchers have observed that the way kratom compounds activate these receptors may reduce the potential for addiction relative to traditional opioids, but “reduced” does not mean zero.
Because kratom is sold as an unregulated product, contamination and inconsistent potency are ongoing concerns. Products may contain more or less of the active compounds than labeled, and some have been found to contain heavy metals or other adulterants. The lack of FDA approval means there are no standardized manufacturing requirements for kratom sold in the U.S.