The drug has been rising in popularity as an opioid alternative. It has been linked with 36 deaths.
Commissioner Scott Gottlieb issued a statement warning about the risks associated with kratom.
For now, kratom is widely available online and in some stores.
The Food and Drug Administration says there's insufficient evidence the supplement works to treat addiction or other problems and cited growing evidence it can be risky.
However, the FDA is not convinced that kratom belongs in unregulated hands. It's also being touted as a way to treat addiction to opioids.
Meanwhile, a similarly troubling trend has been seen with kratom.
Data show that there is harm associated with the use of kratom.
Kratom, or Mitragyna speciosa, is a plant in the coffee family that is native to Southeast Asia.
The scientific research about kratom and its potential medical uses are very limited, but evidence of its risks are clear. He said that calls to USA poison control centers involving kratom increased 10-fold between 2010 and 2015, and that the herb is associated with side effects including seizures, liver damage and withdrawal symptoms.
In some cases reported to the FDA, kratom is laced with opioids like hydrocodone (Vicodin), Gottlieb noted. Gottlieb said the FDA is treating kratom as an unapproved drug and also has taken action against kratom-containing dietary supplements. Instead, Gottlieb mentioned that kratom is already a controlled substance in 16 countries, and that several states have pending legislation to ban it.
"If they find people here who are opening the gates to these drugs, there may be opportunities for the FDA to investigate at a high level", former principal deputy FDA commissioner under the Obama administration, Joshua Sharfstein, told the news site. But the DEA almost made kratom a Schedule 1 drug, the same as heroin and marijuana, last year, and the FDA is now trying to stop shipments of kratom from entering the U.S. while it works on increasing regulatory oversight.
"I want to be clear on one fact: there are now no FDA-approved therapeutic uses of kratom", Gottlieb wrote.
It wasn't the first time. Evidence suggests the stimulants could be similar to ephedrine, a compound derived from ephedra, the unsafe and lethal weight-loss supplement that the FDA banned in 2004. A 2014 report found that more than two-thirds of the supplements purchased six months after being recalled still contained banned drugs.