Insulin Tolerance Test


  • Assess the HPA axis in patients suspected to have secondary (central) adrenal insufficiency.
  • Rule out growth hormone deficiency.


  • CAD or arrhythmia.
  • Stroke or seizure disorder.
  • Age > 60 or < 18.
  • Morning cortisol < 100 (as it may lead to severe and prolonged hypoglycemia, and the insulin tolerance test is likely not required to confirm adrenal insufficiency).


  • The test should be performed in a monitored setting by a qualified physician or nurse, and the patient should be observed throughout the test.
  • Make sure that you have the following available to treat complications:
    • IV hydrocortisone
    • IV dextrose 50%
  • The patient should be instructed not to drive a car after the test. Transportation should be planned in advance.
  • The patient should have a meal available to them to consume after the test is performed.


  1. Insert an IV line.
  2. Obtain baseline glucose, cortisol and growth hormone levels.
  3. Administer regular insulin 0.1 units / kg iv bolus followed by a saline flush.
  4. Obtain glucose, cortisol and growth hormone levels every 20 minutes.
  5. Once glucose is < 2.2 mmol/L and the patient has symptoms of hypoglycemia, administer 25 mL (half an ampule) of 50% dextrose, intravenously.
  6. The patient should have a glucose level > 4 mmol/L before leaving the testing centre.
  • ACTH levels may also be measured.
  • If you suspect severe cortisol and/or GH deficiency and still want to proceed with the test, consider using a lower insulin dose (e.g., 0.05 units/kg).
  • If you suspect insulin resistance (e.g., type 2 diabetes), consider using a higher dose (e.g., 0.15 units/kg).
  • At 40 minute, if the patient does not have symptoms of hypoglycemia and blood glucose remains > 3.5 mmol/L, consider giving a second dose of insulin at 0.05 units / kg (an additional 50% of the initial dose).


  • Cortisol > 500 nmol/L rules out adrenal insufficiency.
  • GH > 5 mcg/L rules out grown hormone deficiency.


  • Hypothyroidism may impair the cortisol response. If the patient was hypothyroid at the time of the test, consider repeating the test after adequate thyroid hormone replacement.

See Also

  • Insuline Tolerance Test in Biomedical Investigations in Laboratory Medicine by J H Barth, G E Butler & P J Hammond.