The JUUL became the most popular e-cigarette in the United States at the end of 2017 and had a market share of 72% as of September 2018. Its widespread use by youth has triggered concern from the public health community and multiple investigations by the U.S. Food and Drug Administration. Given the high nicotine concentrations in JUUL, the nicotine-related health consequences of its use by young people could be more severe than those from their use of other e-cigarette products.