What instructions should be given to patients prior to insulin testing?

Updated: Jan 02, 2019
  • Author: Saranya Buppajarntham, MD; Chief Editor: Eric B Staros, MD  more...
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A 72-hour fasting test is used to identify causes of postabsorptive hypoglycemia. [2] The patient is instructed to fast, and plasma glucose, insulin, proinsulin, and C-peptide levels are measured every 6 hours until the plasma glucose level is less than 65 mg/dL, after which the testing frequency is increased to every 1-2 hours. Fasting is ended when plasma glucose levels are less than 45 mg/dL accompanied by signs and symptoms of hypoglycemia. At the endpoint, a blood sample is collected and tested for glucose, insulin, proinsulin, C-peptide, beta-hydroxybutyrate, and sulfonylurea levels. The patient is given 1 mg of intravenous glucagon, and the response of the blood glucose level is measured.

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