What is the role of glucose tolerance testing (GTT) in preventative medicine?

Updated: May 10, 2021
  • Author: Jiun-Lih Jerry Lin, MBBS, MS(Orth); Chief Editor: Eric B Staros, MD  more...
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A glucose tolerance test can be used to identify patients at high risk of developing type 2 diabetes based on clinical risk factors, with a view to beginning preventive therapy. [4] Approximately 25% of patients with either impaired glucose tolerance or impaired fasting glucose will develop type 2 diabetes over the following 3–5 years. [6] However, the results of a glucose tolerance test cannot distinguish between type 1 and type 2 diabetes mellitus, and cannot be used to predict response to therapy, or likelihood of future complications. [2] Although glucose tolerance testing is more specific than other options, fasting blood glucose and haemoglobin A1c testing are usually more convenient and thus are used more frequently for screening. [4]

Higher plasma glucose levels are linked to increased cardiovascular risk, with this risk increase extending into the non-diabetic range. [7] Impaired glucose tolerance (as demonstrated on a GTT) has also been demonstrated to be a better predictor of increased cardiovascular risk and mortality than fasting glucose. [8, 9]

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