Kratom’s side effects range from mild nausea and constipation at lower doses to seizures, liver injury, and dependence with heavier or prolonged use. The effects depend heavily on how much you take: doses under 5 grams tend to act as a stimulant, while doses between 5 and 15 grams shift toward sedation and pain relief, bringing a sharper risk of adverse reactions. About 20% of regular users who take 5 grams or more report noticeable side effects, most of them gut-related.
How Kratom Acts on the Body
Kratom leaves contain compounds that activate the same receptors in the brain that opioid painkillers target. The plant’s main active ingredient isn’t particularly potent on its own, but your liver converts it into a much stronger form, roughly 10 times more active at opioid receptors. This metabolite is what drives most of kratom’s pain-relieving and sedating effects. Both the original compound and its metabolite are partial activators of opioid receptors, meaning they stimulate the receptor less intensely than full opioids like morphine or fentanyl. They also block other opioid receptor subtypes, which gives kratom a more complex pharmacological profile than a standard painkiller.
This partial activation appears to produce less respiratory depression and less severe constipation compared to traditional opioids, at least based on the receptor signaling pattern involved. That difference likely explains why kratom feels milder than prescription opioids to many users, but it does not make the drug safe, especially at higher doses or when combined with other substances.
Common Side Effects
The most frequently reported side effects are gastrointestinal: nausea, constipation, stomach pain, and loss of appetite. These tend to appear once you cross the 5-gram threshold or use kratom more than about three times per day. At stimulant-level doses (under 5 grams), users more commonly report jitteriness, increased heart rate, irritability, and difficulty sleeping, similar to drinking too much coffee. Kratom is, after all, a botanical relative of the coffee plant.
At sedating doses (5 to 15 grams), additional side effects include drowsiness, dizziness, dry mouth, sweating, and itching. Some people experience brain fog or difficulty concentrating. These effects typically resolve within a few hours but can be more pronounced and longer-lasting in people who are new to the substance or who take it on an empty stomach.
Seizure Risk
Seizures are an uncommon but documented side effect. Among kratom-related cases reported to poison centers and emergency departments, seizure incidence has ranged from about 4.5% to as high as 17.5%, depending on the dataset. A systematic review identified 20 individual cases of seizures following kratom use from published case reports, though the evidence linking kratom directly to seizures is complicated by inconsistent medical records, complex patient histories, and the frequent presence of other substances. Still, the association is consistent enough to take seriously, particularly if you have a history of seizure disorders.
Liver Injury
Kratom can cause liver damage, typically appearing after two to six weeks of regular use. In a clinical study of affected patients, the median time to onset of liver injury was 22 days, with a range of 15 to 49 days. Symptoms included yellowing of the skin and eyes (jaundice), itching, abdominal pain, and fever. The pattern of injury involves both direct damage to liver cells and disruption of bile flow, a combination that can become serious if use continues.
Liver injury from kratom is not common among all users, but it’s unpredictable. There’s no reliable way to know in advance who will develop it. If you notice dark urine, pale stools, persistent nausea, or a yellowish tint to your skin or eyes after starting kratom, those are warning signs of liver involvement.
Dependence and Withdrawal
Because kratom activates opioid receptors, regular use can lead to physical dependence. Your body adjusts to the presence of the drug, and stopping abruptly produces withdrawal symptoms that mirror opioid withdrawal: muscle aches, insomnia, irritability, runny nose, sweating, diarrhea, and cravings. The severity generally correlates with how much you’ve been taking and for how long. People using high doses daily for months tend to experience more intense withdrawal than occasional users.
Tolerance also develops with regular use, meaning you need progressively more to achieve the same effect. This escalation pattern increases your exposure to all of the dose-dependent side effects described above.
Long-Term Physical Changes
Chronic kratom use has been associated with noticeable skin darkening, particularly in sun-exposed areas. This hyperpigmentation is a recognized drug-induced effect, confirmed through skin biopsies in documented cases. Long-term users also commonly report significant weight loss and appetite suppression. These changes can develop gradually over months and may not be immediately obvious to the person using kratom.
Risks From Combining With Other Substances
Mixing kratom with other drugs dramatically increases the danger. CDC data from U.S. poison centers covering 2015 through 2025 shows that 79% of the 233 kratom-associated deaths during that period involved multiple substances. Hospitalization rates were consistently higher when other drugs were present: 44% to 56% of multi-substance cases required hospitalization, compared to 24% to 29% of kratom-only cases.
A key reason for this elevated risk is that kratom strongly inhibits two liver enzymes responsible for breaking down more than half of all marketed drugs, including many opioids, sedatives, and antidepressants. When kratom blocks these enzymes, other drugs stay in your system longer and reach higher concentrations than expected. This can turn a normally tolerable dose of a prescription medication into a dangerous one. Benzodiazepines, opioid painkillers, and sleep medications are particularly risky combinations.
Heavy Metal Contamination
Kratom is sold as a supplement and is not subject to the same quality controls as pharmaceutical drugs. The FDA tested 30 kratom products from various sources and found significant levels of lead and nickel, at concentrations exceeding safe daily exposure limits for oral intake. For heavy users, cumulative exposure could be many times above those limits. Long-term heavy metal accumulation raises the risk of kidney damage, nervous system problems, anemia, high blood pressure, and certain cancers. These risks exist on top of kratom’s own pharmacological side effects and are essentially invisible to the user without blood testing.
Serious Outcomes Are Rising
Reports of serious kratom-related outcomes to U.S. poison centers increased by 1,100% for single-substance exposures between 2015 and 2025, climbing from 76 to 919 cases per year. Multi-substance reports rose 1,300% over the same period. This surge reflects both growing kratom use in the U.S. and increasing awareness among healthcare providers, but the sheer scale of the increase signals a genuine public health pattern rather than just better reporting. Among single-substance kratom exposures, 41% to 49% resulted in outcomes classified as serious, including life-threatening effects and those requiring significant medical treatment.