Kratom acts most similarly to opioids at higher doses and to stimulants like coffee at lower doses. This dual nature makes it unusual among psychoactive plants, and it’s the reason kratom gets compared to such a wide range of substances depending on how much someone takes. Botanically, kratom belongs to the same plant family as coffee, but its active compounds interact with the brain’s opioid receptors in ways that coffee does not.
An Opioid-Like Effect at Higher Doses
The comparison kratom draws most often is to opioids like morphine, codeine, or prescription painkillers. This isn’t just anecdotal. Kratom’s main active compounds, mitragynine and 7-hydroxymitragynine, bind to the same mu-opioid receptors that morphine and fentanyl target. The binding is weaker: morphine latches onto the mu-opioid receptor about 170 times more tightly than mitragynine does. The more potent kratom compound, 7-hydroxymitragynine, has roughly nine times the binding strength of mitragynine but is still about 10 times weaker than morphine at that receptor.
The quality of the effect also differs. Morphine and fentanyl are full agonists at the mu-opioid receptor, meaning they activate it to near-maximum capacity. 7-hydroxymitragynine is only a partial agonist, reaching about 41% of the maximum activation that a full agonist produces. Mitragynine, the most abundant alkaloid in kratom leaves, technically acts as an antagonist at the human mu-opioid receptor in lab tests, meaning it blocks the receptor rather than activating it. In a living body, though, mitragynine gets partially converted into 7-hydroxymitragynine, which likely explains why users still feel opioid-like effects such as pain relief, relaxation, and mild euphoria.
This partial agonist profile makes kratom more comparable to buprenorphine (the active ingredient in Suboxone) than to full opioid agonists like oxycodone or heroin. Both kratom and buprenorphine activate opioid receptors without producing the same ceiling of effect. No formal safety studies have directly compared the two, but the pharmacological parallel is real.
A Stimulant at Lower Doses
At low doses, kratom feels less like an opioid and more like a strong cup of coffee or a mild stimulant. Workers in Southeast Asia have chewed kratom leaves for generations to sustain energy during long days of physical labor, much the way coffee is used elsewhere. This isn’t coincidental: kratom (Mitragyna speciosa) belongs to the Rubiaceae family, the same botanical family as the coffee plant.
The stimulant-like effects appear to involve the adrenergic system, the same network that adrenaline (epinephrine) acts on. Research published in the European Journal of Pharmacology found that mitragynine mimics the action of adrenaline at alpha-2 adrenergic receptors in living animals, though with low potency. Its binding affinity at those receptors is about five times weaker than adrenaline itself. This low-level adrenergic activity, combined with mild opioid receptor interaction, likely produces the increased alertness, sociability, and physical energy that low-dose users describe.
How It Compares to Kava
Kava is the other herbal product kratom gets compared to most frequently, since both are sold as natural mood-altering supplements. The two work through completely different mechanisms and produce different experiences. Kava acts primarily on GABA receptors (the same system targeted by alcohol and anti-anxiety medications), producing sedation and relaxation. Kratom’s effects are more activating, especially at lower doses.
A clinical study of adults who used both products found that 84% of kratom users reported its effects were helpful for meeting daily roles and obligations, compared to just over 50% for kava. Kava’s effects aligned more with recreational relaxation, while kratom was used instrumentally, as a tool for getting through the day. The dependence profiles also diverge: about 38% of regular kratom users in the study met criteria for a substance use disorder, compared to only 7.5% of kava users. Those who used both substances together were more likely to report escalating their kratom dose and using more than they intended.
Withdrawal Feels Like Mild Opioid Withdrawal
Because kratom acts on opioid receptors, stopping after regular use produces withdrawal symptoms that resemble opioid withdrawal, though typically less severe. Documented symptoms include runny nose, insomnia, poor concentration, muscle aches, and flat mood. In one well-documented clinical case, a patient who had previously gone through prescription opioid withdrawal described kratom withdrawal as “considerably less intense but more protracted,” with physician-observed symptoms persisting for about 10 days after the last dose.
For comparison, acute withdrawal from short-acting opioids like oxycodone or heroin typically peaks within 1 to 3 days and resolves within a week, though lingering symptoms can last longer. Kratom withdrawal appears to follow a slower, more drawn-out arc with lower peak intensity.
Not a Perfect Match for Any One Drug
The challenge with comparing kratom to a single substance is that it genuinely doesn’t fit neatly into one category. At low doses it resembles a stimulant. At higher doses it resembles a weak opioid. Its withdrawal profile mirrors opioid dependence but at reduced severity. Its receptor activity looks like buprenorphine’s partial agonism more than morphine’s full activation. And it carries social patterns of use more similar to coffee or energy supplements than to recreational drugs, with most users reporting that it fits into a functional daily routine.
Kratom is not currently a federally scheduled substance in the United States, though the DEA has considered scheduling it and some states have banned it independently. Under federal law, a “controlled substance analogue” is any unscheduled compound that is structurally or pharmacologically similar to a Schedule I or II drug and intended for human consumption. Kratom’s opioid receptor activity puts it in a gray area under this definition, which is part of why its legal status remains contentious.
Toxicity data adds another layer of complexity. In zebrafish embryo studies (a standard model for early toxicity screening), kratom’s main alkaloid mitragynine was actually more toxic to embryos than morphine at comparable concentrations, a finding that surprised researchers given kratom’s reputation as a milder alternative. Whole kratom leaf preparations were less toxic than isolated mitragynine, suggesting that the mix of compounds in the natural leaf may buffer the effects of any single alkaloid. These are early-stage findings in a non-human model, but they challenge the assumption that “natural” automatically means safer.