Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1018 page)

   Not clinically useful for diagnosis of DM

   Interpretation

Increased In

   Insulinoma. Fasting blood insulin level >50 μU/mL in the presence of low or normal blood glucose level. Administration of tolbutamide or leucine causes a rapid rise of blood insulin to very high levels within a few minutes, with a rapid return to normal.

   Factitious hypoglycemia in the presence of normal blood glucose.

   Insulin autoimmune syndrome.

   Untreated mild DM in obese individuals. The fasting blood level is often increased.

   Cirrhosis due to insufficient clearance from blood.

   Acromegaly (especially with active disease) after ingestion of glucose.

   Reactive hypoglycemia after glucose ingestion, particularly with the diabetic type of glucose tolerance curve.

Decreased In

   Type 1 DM.

   Hypopituitarism.

   Severe DM with ketosis and weight loss, which may result in an absence of insulin. In less severe cases, insulin is frequently present but only at lower glucose concentrations.

   Limitations