The Intravenous Glucose Tolerance Test

Two indices of glucose tolerance, the “total index” and the “increment index”, derived from an intravenous glucose tolerance test have been defined, and determined in, 20 normal and 15 diabetic subjects. 2. The “total index” is based on the assumption that the rate of fall of blood glucose remains consistently proportional to the total blood glucose value. The “increment index” assumes that the rate remains proportional to the increment blood glucose value. 3. The mean “total index” for 42 tests in 20 normal individuals was 1·37 and the mean “increment index” was 3·68. 4. The mean “total index” for 21 tests in 15 mildly diabetic patients was 0·71 and the mean “increment index” was 1·83. 5. With a constant loading dose of glucose both indices are reproducible in any one individual. 6. Increasing the loading dose from 25 to 50 g. produced significant increases of the “total index” in 8 normal and 6 diabetic subjects. The “increment index” remained constant in both groups. 7. As the “increment index” is reproducible in any one individual within a twofold variation in the dose of glucose injected, it is the preferable measure of glucose tolerance.