Mitragyna speciosa is the scientific name for kratom, a tropical tree in the coffee family native to Southeast Asia. The tree grows naturally in Thailand, Malaysia, Indonesia, Myanmar, Vietnam, and Papua New Guinea, where its leaves have been used for centuries as both a stimulant and a pain reliever. In recent years, kratom has gained widespread attention in the West as an herbal product, though it occupies a complicated legal and safety landscape.
The Plant Itself
Mitragyna speciosa belongs to the Rubiaceae family, the same botanical family as coffee. In average soil, the tree reaches about 4 to 9 meters tall, but in fertile tropical soil it can grow to 15 to 30 meters. Its leaves are broad and opposite-growing, and it produces compact, round clusters of small flowers. In Thailand, the plant goes by names like kratom, katawan, or tawn. In Malaysia, it’s known as ketum, biak, or kutum.
The psychoactive properties come from alkaloids concentrated in the leaves. The most abundant is mitragynine, which makes up roughly 2% of dried kratom preparations by weight. A second alkaloid, 7-hydroxymitragynine, is far more potent but exists only in trace amounts, typically less than 0.02% of dry leaf weight. Despite its tiny concentration, 7-hydroxymitragynine plays an outsized role in kratom’s effects because of its strong activity at opioid receptors.
How Kratom Works in the Body
Kratom’s effects come primarily from how its alkaloids interact with opioid receptors in the brain. Mitragynine acts as a partial agonist at mu-opioid receptors, the same receptors targeted by morphine and other opioid painkillers. “Partial agonist” means it activates those receptors, but not as fully as a traditional opioid would. 7-Hydroxymitragynine, by contrast, is a full agonist at those same receptors, producing stronger opioid-like effects even though it’s present in much smaller quantities.
But kratom isn’t purely an opioid. Its alkaloids also bind to adrenergic receptors, which are part of the body’s adrenaline signaling system. This dual action on both opioid and adrenaline pathways helps explain why kratom’s effects shift depending on how much you take. At low doses, the adrenergic and stimulant properties tend to dominate. At higher doses, the opioid effects take over.
Dose-Dependent Effects
Kratom’s most distinctive feature is how dramatically its effects change with dose. At low doses of 1 to 5 grams of dried leaf, users typically experience stimulant effects: increased energy, alertness, and sociability. This is how the plant was traditionally used by manual laborers in Southeast Asia, who chewed fresh leaves to combat fatigue during long workdays.
At higher doses of 5 to 15 grams, the experience shifts toward sedation and pain relief, resembling the effects of opioid drugs. Doses above 15 grams can produce effects that look clinically similar to opioid overdose, including dangerous respiratory depression.
Traditional Use in Southeast Asia
The earliest Western documentation of kratom dates to reports submitted to the government of Siam in 1929 and 1934, which noted that kratom didn’t carry the same stigma as opium smoking. But the plant’s use in the region predates those records considerably. Workers chewed the leaves or brewed them into tea for energy, pain relief, and as a treatment for diarrhea. The dose-dependent nature of the plant was well understood: small amounts for work, larger amounts for pain or relaxation.
Side Effects and Safety Concerns
At moderate to high doses, kratom commonly causes nausea, vomiting, sweating, drowsiness, and agitation. Higher doses can trigger more serious effects including rapid heart rate, high blood pressure, tremors, hallucinations, confusion, and seizures. Overdoses can lead to coma and death, particularly when kratom is combined with other substances.
Liver injury is a rarer but well-documented risk. In people who use kratom regularly, liver damage typically appears within 1 to 8 weeks. Early signs include fatigue, nausea, itching, and dark urine, followed by jaundice. The liver injury pattern tends to involve bile flow disruption and can be severe, though it usually resolves on its own once kratom use stops. In serious cases, it can be accompanied by kidney failure.
The FDA has also flagged contamination issues. Some kratom products sold in the U.S. have tested positive for Salmonella bacteria or concerning levels of heavy metals, reflecting the lack of manufacturing oversight for an unregulated product.
Dependence and Withdrawal
Regular kratom use can lead to physical dependence. Because its primary alkaloid acts on opioid receptors, withdrawal looks similar to opioid withdrawal, though generally milder. Symptoms typically start 12 to 48 hours after the last dose and include muscle aches, jerky limb movements, nausea, abdominal cramps, sweating, runny nose, and disturbed sleep. Psychological symptoms like cravings, irritability, anxiety, and depressed mood are also common.
For most people, the worst of withdrawal lasts 1 to 3 days, though some experience symptoms for up to a week. There is no specific diagnostic category for kratom use disorder in the current psychiatric manual, but the pattern of tolerance, dependence, and withdrawal closely mirrors what’s seen with other opioid-like substances.
How the Body Processes Kratom
After ingestion, mitragynine is absorbed quickly, reaching peak blood levels in about an hour. It has a notably long half-life of roughly 45 hours, meaning it stays in your system for days after a single dose. The liver processes mitragynine using a group of enzymes called CYP3A, and one of the byproducts of that metabolism is 7-hydroxymitragynine, the more potent alkaloid. So your body actually converts the weaker compound into the stronger one during digestion.
This metabolic pathway creates a meaningful risk for drug interactions. Kratom alkaloids inhibit two key liver enzyme systems, CYP2D6 and CYP3A, that are responsible for breaking down a wide range of common medications. By slowing those enzymes down, kratom can cause other drugs to build up to higher levels in the bloodstream than expected. Many of the deaths associated with kratom have involved combinations with other substances, likely driven in part by these interactions.
Legal and Regulatory Status
In the United States, kratom is not approved as a drug, a dietary supplement, or a food additive. The FDA considers dietary supplements containing kratom to be adulterated under federal law and has warned consumers against using it, citing risks of liver toxicity, seizures, and substance use disorder. The agency works with U.S. Customs and Border Protection and the Department of Justice to limit imports of kratom products, which are sometimes mislabeled as potpourri or incense to evade detection.
Despite this federal stance, kratom remains widely available in many states through smoke shops, gas stations, and online retailers. State-level regulation varies significantly. Some states have banned it outright, others have passed consumer protection laws regulating its sale, and many have no specific kratom legislation at all. This patchwork means the product’s availability, quality, and labeling vary dramatically depending on where you are.