Kratom effects, dosage and safety: what the research actually reports

This guide summarizes what the published research says about kratom’s reported effects, the amounts people report using, adverse events, dependence and withdrawal. It draws on the large user surveys, poison-centre and medical-examiner data, the Malaysian cohort studies and the regulatory reviews, with sources listed at the end. It is a literature summary for readers trying to understand a confusing public debate. It is not dosing guidance, and it does not recommend kratom for anything; Health Canada has not authorized any kratom product for human consumption, and nothing here changes that.

Last reviewed: November 9, 2026. Part of the KratomSource knowledge base.

The shape of the evidence

Almost everything known about kratom’s effects in people comes from four kinds of source: large online surveys of self-selected users in the United States; field studies of long-term users in Malaysia and Thailand, where fresh-leaf use is traditional; case reports and poison-centre data describing things that went wrong; and a small number of controlled laboratory studies in healthy volunteers that began publishing in the 2020s. There are no large randomized trials. Surveys over-represent people who like kratom enough to answer a survey about it; case reports over-represent harm. Reading both together is the only honest way to describe the picture, and the two sets of sources often disagree.

What users report

The largest survey, by Grundmann (2017), collected 8,049 responses from US kratom users recruited through advocacy organizations and vendors. Respondents were mostly white, aged 31–50, employed, with at least some college; the most common reasons given for use were pain (about two-thirds), emotional or mental health conditions (about two-thirds), and reducing or stopping use of prescription or illicit opioids. A follow-up by Garcia-Romeu and colleagues (2020) at Johns Hopkins, with 2,798 respondents, found a similar profile: 91% cited pain, 67% anxiety, 65% depression, and 41% reported using kratom to cut down on or stop opioids. Coe and colleagues (2019) surveyed 2,867 users with the same pattern.

Described effects are consistently dose-dependent: respondents report increased energy, focus and sociability at smaller amounts and relaxation, pain relief and sedation at larger ones, with the stimulant-like phase fading as amount increases. This matches the receptor pharmacology, where mitragynine’s non-opioid actions appear at lower concentrations and its opioid partial agonism dominates at higher ones; see our pharmacology guide. The most commonly reported unwanted effects in the surveys are nausea, constipation, dizziness and drowsiness, and all become more frequent with larger reported amounts.

What the surveys report about amounts

We include this section because “how much” is one of the most-searched questions about kratom and most of what appears online is vendor copy. What follows is a description of survey findings, not a recommendation; the products surveyed were unstandardized US powders whose alkaloid content was not measured, so the gram figures describe a quantity of leaf of unknown strength.

In Grundmann’s 2017 sample, the majority of respondents reported taking under 5 grams of powder per occasion, one to three times a day. Garcia-Romeu’s 2020 sample reported a similar distribution, and Smith and colleagues’ 2022 dose-effect analysis of regular users found that reported adverse effects, including nausea and next-day fatigue, rose with amount and with frequency. Malaysian field studies describe traditional fresh-leaf use as several leaves chewed or a brewed decoction taken through the working day, which is not directly comparable to dried powder. The Malaysian cohorts also document that long-term daily users escalate over time, a tolerance pattern expected from an opioid-receptor agonist.

Two points matter for a Canadian reader trying to understand labels. First, because alkaloid content varies roughly two-fold across commercial powders, a gram of one product is not a gram of another in any pharmacological sense; a certificate of analysis showing mitragynine percentage is the only way to compare. Second, extracts and 7-hydroxymitragynine products concentrate alkaloids by five- to fifty-fold or more and the survey literature above does not describe them; our 7-OH guide explains why regulators treat them separately.

Adverse events in the record

Poison centres

Post and colleagues (2019) reviewed 1,807 kratom exposures reported to US poison centres between 2011 and 2017. Reports rose sharply over the period. About two-thirds involved kratom alone; the most common effects were agitation, rapid heart rate, drowsiness, nausea and high blood pressure, and serious outcomes (seizures, coma, respiratory depression) were concentrated in cases involving other substances. Eleven deaths were recorded in the dataset, two of them with kratom as the only substance reported.

Deaths

The US CDC examined 27,338 unintentional overdose deaths from July 2016 to December 2017 in states with detailed toxicology. Kratom was detected in 152 (0.56%) and was listed by a medical examiner as a cause of death in 91. Of the 152, fentanyl or fentanyl analogues were present in 65%, heroin in 33%, benzodiazepines in 22%, and prescription opioids in 20%. Seven deaths had kratom as the only substance detected, though the authors note other substances could have been present and untested. The FDA has separately described 44 deaths it associates with kratom, most involving other drugs or adulterated products. The fair summary is that kratom-only deaths are rare and documented, and that most recorded deaths involve kratom combined with opioids or sedatives.

Liver injury

Case reports since 2011 describe a cholestatic pattern of liver injury in a small number of users, typically beginning two to eight weeks after regular use started, with jaundice, itching and dark urine, and resolving on stopping. The US National Institutes of Health LiverTox database rates kratom as a probable cause of clinically apparent liver injury. Schimmel and Dart’s 2020 review counted several dozen published cases. The mechanism is unknown and the rate cannot be estimated from case reports; it is clearly uncommon relative to the number of users but not zero.

Seizures, heart rhythm, pregnancy

Seizures appear in poison-centre data and case reports, most often with co-ingestants. Prolonged QT interval, a heart-rhythm finding, has been described in case reports and in one controlled study at higher exposures. Neonatal abstinence syndrome, a withdrawal syndrome in newborns, has been reported in infants born to people who used kratom daily during pregnancy, with the newborns treated the same way as for opioid exposure.

Contaminated products

Some harm attributed to kratom is harm from what was in the bag alongside it. The 2018 US salmonella outbreak sickened 199 people across 41 states. FDA testing of 30 products in 2019 found lead and nickel at levels that, for a heavy daily user, exceeded safe exposure. Studies of commercial products have found 7-hydroxymitragynine at levels above anything leaf produces, suggesting deliberate spiking. These are the risks that lab testing addresses directly, and the reason our vendor rankings weight lab transparency as heavily as they do; see lab testing explained.

Dependence and withdrawal

Regular daily use produces tolerance and a withdrawal syndrome. Singh, Müller and Vicknasingam (2014) interviewed 293 regular users in Malaysia and found that most long-term daily users experienced withdrawal on stopping: muscle aches, insomnia, irritability, runny nose, restlessness and low mood, generally described as moderate and lasting from a few days to about a week. In the Garcia-Romeu survey, 9.5% of respondents reported withdrawal symptoms and about 12% met DSM-5 criteria for a mild kratom-related substance use disorder, with smaller proportions meeting moderate or severe criteria; most respondents did not meet criteria. Henningfield and colleagues’ 2018 eight-factor analysis for the FDA, which was industry-funded, concluded that kratom’s abuse potential resembled caffeine or nicotine more than classical opioids; the FDA’s own 2017–2018 analysis reached the opposite conclusion and recommended controlling it. The WHO Expert Committee on Drug Dependence, reviewing the same literature in 2021, found the evidence insufficient to recommend international control and asked for continued monitoring.

Cases of severe withdrawal and of kratom use disorder requiring treatment are documented, including treatment with buprenorphine. Whether kratom helps or harms people who use it to leave opioids is unresolved: the surveys describe many respondents who say it helped them stop, and the clinical literature describes people who substituted one dependence for another. Both are real populations and the research cannot yet say how large each is.

Interactions

Mitragynine inhibits the liver enzymes CYP3A4 and CYP2D6 in laboratory studies, which raises the possibility of altered blood levels of medications processed by those enzymes. Case reports describe serious outcomes when kratom was combined with other sedatives, with the antipsychotic quetiapine, with certain antidepressants, and with modafinil (a reported seizure). Combining it with alcohol, benzodiazepines or opioids adds sedative and respiratory effects. None of this is characterized well enough to list “safe” and “unsafe” combinations, which is why every credible source says that anyone taking medication should involve a physician or pharmacist in any decision about kratom.

What regulators say

• Health Canada has not authorized any kratom product for sale as a natural health product or drug and has stated that kratom may pose serious health risks when consumed; it has seized products marketed for consumption. Sale as a botanical not for consumption is the grey zone Canadian vendors operate in. See our legal guide and the enforcement tracker.
• US FDA states kratom has no approved medical use, has issued import alerts and warning letters, and in 2025–2026 moved to control concentrated 7-hydroxymitragynine while leaving leaf unscheduled federally.
• WHO (2021) found insufficient evidence for international scheduling and recommended surveillance.
• Thailand decriminalized in 2021 and regulates sale with age limits; Indonesia regulates export quality since 2024; Malaysia prohibits.

Where to get help

If you or someone you know is having trouble with kratom or any substance, Canadian provincial health lines (811 in most provinces) and the national Wellness Together Canada service can connect you with support. In an emergency, call 911. Poison centres across Canada can be reached through the national line at 1-844-POISON-X (1-844-764-7669).

Sources

• Grundmann O. Patterns of kratom use and health impact in the US: results from an online survey. Drug Alcohol Depend 2017;176:63–70. PubMed 28521200.
• Garcia-Romeu A, Cox DJ, Smith KE, Dunn KE, Griffiths RR. Kratom (Mitragyna speciosa): user demographics, use patterns, and implications for the opioid epidemic. Drug Alcohol Depend 2020;208:107849.
• Coe MA, Pillitteri JL, Sembower MA, Gerlach KK, Henningfield JE. Kratom as a substitute for opioids: results from an online survey. Drug Alcohol Depend 2019;202:24–32.
• Smith KE et al. Searching for a signal: self-reported kratom dose-effect relationships among a sample of US adults with regular kratom use histories. Front Pharmacol 2022;13:765917.
• Post S, Spiller HA, Chounthirath T, Smith GA. Kratom exposures reported to United States poison control centers: 2011–2017. Clin Toxicol 2019;57(10):847–854.
• Olsen EO et al. Unintentional drug overdose deaths with kratom detected, 27 states, July 2016–December 2017. MMWR 2019;68(14):326–327. CDC.
• Singh D, Müller CP, Vicknasingam BK. Kratom (Mitragyna speciosa) dependence, withdrawal symptoms and craving in regular users. Drug Alcohol Depend 2014;139:132–137.
• Schimmel J, Dart RC. Kratom (Mitragyna speciosa) liver injury: a comprehensive review. Drugs 2020;80:263–283. NIH LiverTox, Kratom.
• Henningfield JE, Fant RV, Wang DW. The abuse potential of kratom according to the 8 factors of the Controlled Substances Act. Psychopharmacology 2018;235:573–589.
• WHO Expert Committee on Drug Dependence, 44th meeting (October 2021), kratom pre-review report.
• CDC, Multistate outbreak of Salmonella infections linked to kratom, 2018. FDA, FDA and Kratom (heavy-metal testing, adverse event statements).
• Health Canada, kratom advisories and product seizures (Recalls and Safety Alerts database).

Frequently asked questions

What effects do kratom users report?

Large US surveys report dose-dependent effects: increased energy and focus at smaller amounts, relaxation, pain relief and sedation at larger ones. The most common unwanted effects are nausea, constipation, dizziness and drowsiness.

How much kratom do people take?

This guide describes survey findings only, not recommendations. In the largest survey most respondents reported under 5 grams of unstandardized powder per occasion, one to three times daily, with adverse effects rising with amount and frequency.

Has anyone died from kratom?

The US CDC found kratom detected in 152 of 27,338 overdose deaths (0.56%) in 2016–2017, with seven involving kratom alone. Most recorded deaths involved fentanyl, heroin, benzodiazepines or other drugs.

Is kratom addictive?

Regular daily use produces tolerance and a withdrawal syndrome described as generally milder than opioid withdrawal. In a 2020 survey about 12% of respondents met criteria for mild kratom use disorder; most did not.

Can kratom damage the liver?

Case reports describe a cholestatic liver injury in a small number of users, usually starting weeks into regular use and resolving on stopping. NIH LiverTox rates kratom a probable cause. The rate is unknown but uncommon.