A year over year comparison of submitted mitragynine blood cases to the laboratory shows a 53% increase in 2018 (n=785) compared to 2017 (n=512). 

Donna M Papsun, Ayako Chan-Hosokawa, Laura Friederich, Justin Brower, Kristopher Graf, Barry Logan, The Trouble With Kratom: Analytical and Interpretative Issues Involving Mitragynine, Journal of Analytical Toxicology, Volume 43, Issue 8, October 2019, Pages 615–629, https://doi.org/10.1093/jat/bkz064