A 60-year-old woman with a lithium intoxication presented initially to the emergency department with a Glasgow coma scale (GCS) of 15/15. With initial conservative treatment (hydratation) she developed coma, necessitating haemodialysis. During haemodialysis there was no clinical improvement although there was a drop in the serum lithium levels. However, neurological recovery occurred after the first haemodialysis session, while the Lithium level rose again. This case illustrates initial clinical deterioration despite decreasing lithium levels as well as consequent clinical improvement without drop in lithium levels. This case also illustrates the pharmacokinetic profile of lithium and supports the use of primarily clinical signs completed with serum levels of lithium to determine the severity of a lithium poisoning and the adequate therapy including dialysis.