Post-mortem biochemistry, also called thanatochemistry, has proved useful in forensics for estimating the time since death and assessing the cause of death. Ketoacidosis is a frequent complication of diabetes mellitus which can be lethal, with possible medicolegal implications. However, interpretation of biochemical analyses is difficult because of post-mortem blood alterations involving glucose metabolic pathways. Vitreous humor is better preserved than blood after death, and therefore is preferentially used in thanatochemistry. However, both the lack of experience of most biochemists with this matrix in clinical practice, and the paucity of post-mortem studies make interpretation of post-mortem analyses difficult. This review examines the recent advances in the knowledge of glucose metabolism in vitreous humor, and the methods used for the post-mortem diagnosis of diabetic complications.