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Insulin Tolerance Blood Test

Last updated Nov. 7, 2018

The Insulin Tolerance Blood Test is performed by administering a dose of insulin via IV. Blood samples are taken just before the insulin administration, and 30 and 45 minutes after insulin is administered.


What are other Names for this Test? (Equivalent Terms)

  • Insulin Resistance Blood Test
  • IR Blood Test
  • ITT Blood Test

What is Insulin Tolerance Blood Test? (Background Information)

  • Insulin is a hormone produced by the beta cells of the pancreas. It causes cells to take in glucose, thereby reducing blood sugar levels
  • Insulin tolerance, or insulin resistance, refers to the tendency of cells to resist the effects of insulin. This causes an abnormally high blood sugar level, which may result in kidney damage and other conditions related to prediabetes
  • An abnormal insulin tolerance may also be due to a hormone-secreting tumor or problems with the pituitary gland, all of which interfere with insulin production
  • The Insulin Tolerance Blood Test estimates an individual’s insulin tolerance. It helps diagnose neuroendocrine tumors and prediabetes or type II diabetes
  • The Insulin Tolerance Blood Test is performed by administering a dose of insulin via IV. Blood samples are taken just before the insulin administration, and 30 and 45 minutes after insulin is administered. The samples are then analyzed for glucose levels

What are the Clinical Indications for performing the Insulin Tolerance Blood Test?

Following are the clinical indications for performing the Insulin Tolerance Blood Test:

  • Excessive thirst
  • Rapid weight change
  • Fatigue
  • Vision problems
  • Frequent and persistent infections
  • Easy bruising

How is the Specimen Collected for Insulin Tolerance Blood Test?

Following is the specimen collection process for Insulin Tolerance Blood Test:

Sample required: Blood

Process of obtaining a blood sample in adults:

  • A band is wrapped around the arm, 3-4 inches above the collection site (superficial vein that lies within the elbow pit)
  • The site is cleaned with 70% alcohol in an outward spiral, away from the zone of needle insertion
  • The needle cap is removed and is held in line with the vein, pulling the skin tight
  • With a small and quick thrust, the vein is penetrated using the needle
  • The required amount of blood sample is collected by pulling the plunger of the syringe out slowly
  • The wrap band is removed, gauze is placed on the collection site, and the needle is removed
  • The blood is immediately transferred into the blood container, which has the appropriate preservative/clot activator/anti-coagulant
  • The syringe and the needle are disposed into the appropriate “sharp container” for safe and hygienic disposal

Preparation required: No special preparation is needed prior to the test.

What is the Significance of the Insulin Tolerance Blood Test Result?

The significance of the Insulin Tolerance Blood Test result is explained.

  • A high value (blood glucose that falls less than 25% and returns rapidly to fasting level) for the test may indicate:
    • Acromegaly
    • Cushing syndrome
    • Dermatomyositis 
  • A low value for the test may indicate:
    • Hypoglycemic unresponsiveness
    • Pancreatic islet cell tumor
    • Adrenocortical insufficiency
    • Hypothyroidism
    • von Gierke disease

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • The Insulin Tolerance Blood Test should be avoided under the following situations (i.e., the test is contraindicated for):
    • In individuals over 60 years old
    • In individuals with severe hypothyroidism
    • In individuals with ischemic heart diseases (such as congestive heart failure or previous history of heart attacks)
    • The test should not be performed in children without the close supervision of a pediatric healthcare professional
  • Certain factors may interfere with the results of the test. These include diet, hydration status, and menstruation

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


Helpful Peer-Reviewed Medical Articles:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: June 2, 2016
Last updated: Nov. 7, 2018