The America’s Poison Centres National Poison Data System (NPDS) is set up for the active surveillance of voluntarily reported poisoning cases in near real-time. The Centres for Disease Control and Prevention (CDC)’s Wide-ranging Online Data for Epidemiologic Research (WONDER) database is final national mortality data from state registries. We compared suicide poisoning deaths in both datasets from 2000 to 2020 and tested their relationship using a simple linear regression model. Mean annual suicide poisoning deaths during the review period were 699 (SD 145) in NPDS, and 6150 (SD 577) in WONDER. NPDS annual cases averaged 11% of cases recorded in WONDER (SD 2%; Range 8%–16%). The regression coefficient for the linear relationship between annual deaths recorded in both datasets was 0.18 (p-value<0.001, R2=0.51). The rapidly available NPDS data on fatal self-poisoning may provide sentinel surveillance regarding self-poisonings, but do not reliably predict final national data on suicide poisoning.