Isopropanol (IPA) detected in deaths because of diabetic ketoacidosis (DKA) or alcoholic ketoacidosis (AKA) may cause concern for IPA poisoning. This study addressed this concern in a 15-year retrospective review of 260 deaths in which concentrations of acetone and IPA, as well as their ratios, were compared in DKA (175 cases), AKA (79 cases), and IPA intoxication (six cases). The results demonstrated the frequency of detecting IPA in ketoacidosis when there was no evidence of IPA ingestion. IPA was detectable in 77% of DKA cases with quantifiable concentrations averaging 15.1 ± 13.0 mg/dL; 52% of AKA cases with quantifiable concentrations averaging 18.5 ± 22.1 mg/dL; and in cases of IPA intoxication, averaging 326 ± 260 mg/dL. There was weak correlation of IPA production with postmortem interval in DKA only (r = -0.48). Although IPA concentrations were much higher with ingestion, potentially toxic concentrations were achievable in DKA without known ingestion.