Background: The mood stabilizer lithium has a narrow therapeutic index with a relevant risk of intoxication. We used real-world hospital data to identify causes, treatment courses, and outcomes of high lithium levels and intoxications. Methods: Retrospective chart review of patients with a lithium concentration of ⩾1.1 mmol/L, who were treated at Charité University Medical Center Berlin. Results: We identified 136 patients (58% women; mean age: 54.7 years) with high lithium levels or intoxication. 66.9% were chronic (stable lithium dose but changes in other variables such as co-medication). 40.4% took at least one risk medication with a relative contraindication for concurrent lithium treatment. 11.1% of the cases with a high therapeutic level showed moderate to severe intoxications. Feverish infections were significantly associated with severe intoxications. Overall, 97.1% (132/136) of patients fully recovered, two had residual but mild symptoms and two died during hospitalization (unlikely related to the intoxication). In 37.5% of patients, no psychiatrist was involved in the management of high lithium levels or intoxication. In these patients, lithium treatment was adjusted or discontinued in 37.3% of the cases compared to 64.7% when a psychiatrist was involved (χ²(1) = 9.683, p = 0.002). Conclusions: Patients and medical doctors should be aware of the increased risk of lithium intoxication already within the high therapeutic range and should consider alternative medications without relative contraindications for concurrent lithium use. Involving psychiatrists during or after an intoxication event is associated with more frequent adjustment of the maintenance lithium dose and should be considered in most cases.