The herbal supplement kratom, made from the leaves of a Southeast Asian plant and used by some to manage the pain of opioid withdrawal, has been the source of a growing number of calls to poison control centers in the United States. The centers reported 1,807 calls in a seven-year span, rising from 13 in 2011 to 682 in 2017, according to research published in the journal Clinical Toxicology. Sixty-five percent of those calls were made in 2016 and 2017. Kratom is legal in most states but not regulated by the Food and Drug Administration because it is a supplement, not a drug. Besides being used to relieve pain or ease the effects of opioid withdrawal, it also is taken as a mood booster to help with anxiety or depression. It is usually taken as a pill or capsule, according to the National Institute on Drug Abuse, but some people chew kratom leaves or brew them into a tea.