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From Abingdon, Viginia, USA:

I recently had a four hour oral glucose tolerance test (OGTT) that resulted in a severe hypoglycemic reaction five minutes before the fourth hour. I also had blood drawn for insulin while fasting and, then, every time blood was drawn, to check glucose. My fasting glucose was 103 mg/dl [5.7 mmol/L] and my fasting insulin was 3.0. I had fasted for 12 and a half hours. I had to do quite a bit of walking that morning to get to the building, which was about one-fourth of a mile and wonder if this could have brought down my glucose and insulin level very much as diabetes had been suspected. As for the rest of the test, at 30 minutes, my blood glucose was 161 mg/dl [8.9 mmol/L], insulin 22.1. At one hour, my blood glucose was 155 mg/dl [8.6 mmol/L], insulin 72.9. At two hours my blood glucose was at 113 mg/dl [6.3 mmol/L], insulin 81.4. At three hours, my blood glucose was at 84 mg/dl [4.7 mmol/L], insulin 32.9. At four hours, my blood glucose was at a low of 51 mg/dl [2.8 mmol/L] and my insulin was at a low of 5.6. I don't understand why my blood glucose was within normal range and my insulin was low that morning and then what occurred with the levels of both during my test. Could you help me understand the results? It is some time before I see my doctor.


There is a condition called reactive hypoglycemia where a person having this problem tends to develop low blood sugars in response to a high carbohydrate meal load (similar to taking oral glucose). It is almost as if the body has a difficult time with the braking mechanisms trying to slow insulin down as the glucose falls. The problem with the four hour test is that it is neither necessary or specific for this diagnosis. Previous studies have shown that these findings are not specific for this condition. A lot of people who are otherwise normal have this response on a prolonged OGTT.

I would ask why the OGTT was being performed. If it were for the diagnosis of diabetes, the usual test would be to perform the two hour 75 gram oral glucose tolerance test. Your results did not show evidence of diabetes. If you are not having problems with low sugars after meals, I would not be too excited about it. If this is a problem, the test is not necessary to make the diagnosis. The next response would be to work with the dietitian on decreasing the carbohydrate load at meals and try small, frequent feedings throughout the day. The problem tends to go away with time.


Original posting 22 Jan 2008
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