Case presentation

A 57-year-old female with a history of chronic alcoholic pancreatitis status post partial pancreatectomy, presumed type 2 diabetes mellitus, polysubstance use disorder, intravenous drug use, chronic spinal stenosis, and anxiety presented to the emergency department with severe uncontrolled hyperglycemia and worsening lower back pain following several recent falls. She also reported chills, polyuria, and shortness of breath but denied fever, nausea, vomiting, chest pain, abdominal pain, constipation, or diarrhea. The patient admitted that she was not taking any prescribed medications, including antihyperglycemic therapy, despite her history of diabetes mellitus.

Initial laboratory evaluation demonstrated severe hyperglycemia with a serum glucose level of 668 mg/dL (reference range = 74-106 mg/dL). Hemoglobin A1c was markedly elevated at 19%, consistent with longstanding poor glycemic control. Endocrine evaluation revealed a low C-peptide level of 0.87 ng/mL (reference range = 1.1-4.4 ng/mL), as summarized in Table 1. Serum insulin was within the reference range at 9.4 μIU/mL (reference range = 2.6-24.9 μIU/mL); however, the sample was obtained after initiation of exogenous insulin therapy and therefore did not reflect endogenous insulin secretion. The patient's history of chronic alcoholic pancreatitis, prior partial pancreatectomy, and low C-peptide level made pancreatogenic (type 3c) diabetes the most likely diagnosis.

Laboratory test | Patient's result | Reference range | Clinical interpretation
Serum glucose | 668 mg/dL | 74-106 mg/dL | Severe hyperglycemia
Hemoglobin A1c | 19.0% | <5.7% | Consistent with longstanding poor glycemic control
C-peptide | 0.87 ng/mL | 1.1-4.4 ng/mL | Decreased endogenous insulin production
Serum insulin | 9.4 μIU/mL | 2.6-24.9 μIU/mL | Within reference range; interpretation limited by exogenous insulin administration

During hospitalization, the patient underwent repeated counseling regarding the importance of glycemic control and insulin adherence. Multiple insulin regimens, including premixed insulin and basal-bolus therapy, were attempted; however, glycemic control remained poor because of repeated refusal of insulin administration.