This depends who you ask. As we said there are many proponents of it out there, but there are also those who think it is dangerous. Webmd states that “Kratom is possibly unsafe for most people”. It has several possible side effects such as nausea, dry mouth, tongue numbness, constipation, aggression, hallucinations, delusions, and thyroid problems. In large doses it has been linked to brain swelling, trouble breathing, seizure, liver damage, and even death. However, most deaths surrounding Kratom also involved other drugs (see drugabuse.gov).
Side effects seem to increase in severity depending on the amount of Kratom taken as well as the users age, size, health, and body composition. Since it is unregulated there are no official dosing recommendations so it is best to start with a very small amount to test your tolerance.
It is possible that Kratom might cause dependence, which means that users can feel physical withdrawal symptoms when they stop taking it. This is something to consider before using.