The purpose of this study was to evaluate the severity of lithium poisoning from a poison control center–based population and the correlation of the Hansen and Amdisen classification with outcome and lithium levels in that setting. All lithium overdoses brought to the attention of the poison control center were prospectively observed during 1 year. Demographic data, amount ingested, coingestants, symptoms and signs, lithium levels, treatment, and outcome were recorded. There were 12 acute lithium overdoses: 5, 5, and 2 with grade 0, 1, and 2, respectively. No patients required hemodialysis or had sequelae or died. There were 174 acute-on-chronic overdoses: 66, 85, 15, and 8 with grade 0, 1, 2, and 3, respectively. Six patients underwent hemodialysis; none had sequelae but one died. There were 19 chronic poisonings: 9, 9, and 1 with grade 1, 2, and 3, respectively. Three patients underwent hemodialysis; one had sequelae and one died. Patients classified as grade 2 had higher lithium levels than those with grade 1 in patients with only lithium poisoning (3.08 ± 0.77 vs. 2.09 ± 0.91 mmol/L P = 0.03).The study concluded that morbidity (0.5%) and mortality (1%) associated with lithium poisoning are rarely observed. The Hansen and Amdisen classification does not appear to be a useful clinical tool to predict either morbidity or mortality and does not correlate well with lithium levels.