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I would like to know how to interpret my three year old son's glucose tolerance test. The doctors didn't give us much information besides that it was "subnormal", and they didn't give us normal ranges. His results were:

Time Glucose Insulin C-peptide
Baseline 65 mg/dl [3.6 mmol/L] 3.7 0.3
30 minutes 95 mg/dl [5.3 mmol/L] 12.8 0.7
60 minutes 100 mg/dl [5.6 mmol/L] 10.4 1.8
2 hours 95 mg/dl [5.3 mmol/L] 13.1 1.6
3 hours 57 mg/dl [3.2 mmol/L] 4.5 2.0

My son has had this same problem for about 2 years now has had many, many episodes of low blood sugars (20s to 40s mg/dl [1.1 to 2.2 mmol/L]) and high blood sugars (200s to 400s mg/dl [11.1 to 22.2 mmol/L]). He has had this same problem for about two years. Just last weekend, he fell to 45 mg/dl [2.5 mmol/L] about 30 minutes after eating cereal and milk! They did a 24 hour fast, and, at the last minute, e fell to 51 mg/dl [2.6 mmol/L] which they said was normal.The doctors aren't sure whether my son is developing diabetes or has a metabolic disorder.

Do you see this type of GTT in children with pre-clinical diabetes? Does diabetes take this long to come out? Are low blood sugars common early on?


It is difficult to interpret a rather elaborate test like this without knowing exactly how much glucose he had. At first glance, the serum levels all appear to be within normal limits and are 'subnormal' only in the sense that they are in the lower range of normal. The insulin and C-peptide levels look low; but that could relate to a low glucose load. In any case, by far the most widely standardised test for what is called a diminished 'first phase insulin release (FPIR)' in this age group is an intravenous glucose tolerance test with 1 and 3 minute serum insulin and/or C-peptide levels; but it is a little more difficult to administer technically.

Since you seem mainly concerned with the possibility of pre-diabetes despite the very normal fasting blood sugar levels by far the best test you could have done would be an antibody test for typeá1A or autoimmune diabetes, especially if your son has a Caucasian background. (Call 1-800-425-8361 for the nearest laboratory center) This test might be negative in a child who was Hispanic or African American but here, if you really thought it necessary, you might be able to predict later clinical typeá1B or idiopathic diabetes by a diminished FPIR.

In both forms of typeá1 diabetes, blood sugars are high fasting and rise after a meal, but, in three hours or so, they can swing to being too low because of the delayed insulin response to a glucose load.

If the antibody test is negative and he has symptoms with the low blood sugars, it would be appropriate to consider metabolic causes of hypoglycemia, in particular disorders of organic acid metabolism which does require rather specialised laboratory facilities.


Original posting 13 Jul 2001
Posted to Diagnosis and Symptoms


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Last Updated: Tuesday April 06, 2010 15:09:24
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