Suicide is one of the leading causes of death today, and among all mental illness, mood disorders account for one of the main risk factors. It is well known and proven that suicides are very common among people undergoing treatment and prescribed psychiatric medication. So far, however, there have only been a few studies dealing with this particular phenomenon. For this reason, autopsy patients who died by suicide, suffered from a mood disorder, and were known to be taking psychiatric medication at the time of death were selected for this study. The blood and urine samples taken during the autopsy underwent toxicological analysis and the results were compared with the prescribed therapy. A total of 22 people were included in the study: 12 presenting with depression and 10 with bipolar disorder. The toxicological analysis revealed that only 6 cases (27%) showed a qualitative match with the prescribed medication. In 5 cases (22.7%) the medication was only partially complied with and in 11 cases (50%) it was not complied with at all. Furthermore, even when medication was present, the value was often below the therapeutic range. Overall, more than 70% of the test subjects adhered to their medication only partially or not at all. Since treatment adherence is considered as a key factor in reducing the risk of suicide, this inevitably raises relevant clinical and forensic questions. Against this background, prospective monitoring of post-mortem medication levels in suicidal individuals and synergistic collaboration between clinicians and forensic pathologists could help to evaluate the effectiveness of specific medical interventions, highlight existing critical problems and develop new approaches to suicide prevention.