What Does My Oral Glucose Tolerance Test Results Indicate?
FBS = 90; HgbA1c = 4.1
Glucose tolerance, 1 hour = 245 mg/dL;
Glucose tolerance, 2 hour = 97 mg/dL;
Insulin Ab #1 = 25.5; C-peptide #1 = 4.97
Insulin Ab #2 = >300; C-peptide #2 = >20.
Insulin Ab #3 = 77.6; C-peptide # 3 = 13.8
Based upon current standard criteria for the diagnosis of diabetes, you do not have diabetes.
But I would like to ascertain if the test was performed correctly ie were you given 75 grams of glucose in water to drink after taking the fasting sample?
If not, then the test was conducted according to established guidelines.
Furthermore, there is no role of insulin antibodies when glucoses are normal like in your case. These are performed only in select situations such as in those in whom type 1 diabetes is suspected, and in those experiencing low glucose reactions when they do not have diabetes.
C peptide is also now mostly a research test. It adds little information to the diagnosis of diabetes for the common real life practice scenarios.
There is no current recommendation to test C peptide in an individual with normal glucoses
Does this mean that I have prevented the development of diabetes because of diet modification? If yes, I will continue on this low-carb lifestyle. FYI, I didn't change anything else in my life, and didn't exercise.
Do you think I have insulin resistance or pre-diabetes? Isn't the 1-hour glucose tolerance test (245 mg/dL) abnormal? Should I be worried about this?
Yes whatever lifestyle change you have made seems to have lowered your fasting glucose. Dietary modification alone can do so too, even without exercise.
However, low carb is not the only type of dietary change that is associated with improvement in blood glucoses. This has been studied extensively and it has been found that essentially lowering intake of calories does the job, with or without increased expenditure of calories through physical activity.
It is likely you have insulin resistance. With the current practice guidelines there is no need to measure insulin levels to prove this. Moreover, the current standard cutoffs for the diagnosis of diabetes and pre diabetes are based upon fasting and 2 hour glucose values. I agree your 1 hour value is high but again this has not been studied as widely as the 2 hour reading