What is a glycemic index examination?

A glycemic index or curve of oral glucose is a test used to diagnose diabetes mellitus. It measures how carbohydrates are converted into glucose in the body (how food raises blood sugar) and is usually done in 2 blood draws, one before ingestion of the glucose solution and one two hours after. The glycemic index examination is also used during pregnancy to screen for gestational diabetes and in this case the draws are 3, before, one hour after, and two hours after the glucose solution is ingested.


What is the purpose of a glycemic index examination?

A glucose index examination allows the doctor to identify an abnormal carbohydrate metabolism.
In particular blood glucose level is considered to be normal if two hours after the glucose solution is ingested the level remains below 140 mg/dl. For values between 140 mg/dl and 200 mg/dl the patient is said to have impaired glucose tolerance which is a condition of pre-diabetes, and for any value above 200 mg/dl the patient is diagnosed with diabetes mellitus.
For gestational diabetes however the parameters are different. Values below 92 mg/dl before the glucose solution, lower than 180 mg/dl after one hour and less than 153 mg/dl after two hours of the glucose solution ingestion indicate a normal health state.
It is important to monitor these values for an indication of the health of the patient, or mother and unborn child.


Are there any guidelines for preparation?

The examination is performed early in the morning on an empty stomach.


Who should take a glycemic index examination?

Patients with values above 100 mg/dL, but less than 126 mg/dl on the glycemic index before the solution ingestion should carry out the examination. Values of glucose level below 100 mg/dl during the initial phase are considered normal. Two values of pre-ingestion glucose level greater than 126 mg/dl, or a single value at any time of the day higher than 200 mg/dl, are diagnosed as diabetes mellitus. The examination should also be taken by pregnant women who are at risk of developing gestational diabetes if their gynecologist advises them so. 


Is a glycemic index examination dangerous or painful?

A glycemic index examination is a simple and non-invasive examination. The only discomfort may stem from the very sweet flavor of the glucose solution, which in more sensitive patients can induce nausea.


How is a glycemic index examination carried out?

An initial blood test measures the values at normal state. The patient is then asked to drink a glucose solution composed of water and 75 grams of sugar, and another blood sample is taken two hours later. In the case of testing for gestational diabetes there is an additional test at the one hour interval.