Glucose Tolerance Test with Insulin (GTT / IGTT)

Time

Normal Glucose Values

Normal Insulin Values

What the Results Mean

Fasting

< 126 mg/dl

< 10 mIU/ml

Normal glucose results are 70-90, 111 or over is impaired, 126 or over is diabetic. Insulin levels above 10 show insulin resistance.

½ hour

< 200 mg/dl

40-70 mIU/ml

A truly normal glucose response will not exceed 150.

1 hour

< 200 mg/dl

50-90 mIU/ml

Some want to lower the threshold on glucose to < 180 to identify early stages of diabetes. Insulin > 80 shows insulin resistance, or a level 5 times that of the fasting level (i.e., a fasting of 11 followed by a 1 hour > 55)

2 hours

< 140 mg/dl

6-50 mIU/ml

A truly normal glucose response is 110 or lower.
Insulin > 60 is IR.

3 hours

< 120 mg/dl

4 hours

< 120 mg/dl