Fatal Insulin Overdoses: Case Report and Update on Testing Methodology

Suicidal insulin overdoses are an under-recognized and uncommon cause of death, often relying on scene and nonspecific autopsy findings. Here, we present a case report of a fatal exogenous insulin overdose in a patient with type 1 diabetes. In our case, there were no contributory autopsy findings; however, serum analog aspart insulin levels were c. 10× the predicted therapeutic upper limit (4000, reference 6.6-55 uU/mL), which correlated with scene findings. This was specifically determined by a newly developed immunocapture liquid chromatography-tandem mass spectrometry assay, able to discriminate between various synthetic insulin analogs. Total insulin levels by immunoassay were highly elevated on the Siemens Advia Centaur, but not the Roche platforms (4741 vs. 5.2 uU/mL, respectively), showing variable sensitivity of detection within the same analog depending on assay. We discuss the prevalence and features to look for at autopsy in these types of cases. Additionally, analytical options for testing insulin levels, including new methodologies, guidance on collection of samples, as well as an outline of available historical reference range data are discussed.