does a high value at one hour during a GTT mean you have diabetes?

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December 13, 2005

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Question

If your blood sugar is greater than 200 mg/dL [11.1 mmol/L] at the first hour of an oral glucose tolerance test but not at the second hour, does this mean you have diabetes or just impaired glucose tolerance? When the ADA standard states "any casual test greater than 200 mg/dL [11.1 mmol/L]" is positive for diabetes does that first hour of the OGTT count as causal?

Answer

In rare circumstances, a very high reading at the one-hour mark during an OGTT might not be diabetes. For example, there's a syndrome of "dumping" that happens in some people with abnormal stomach function where the sugar goes right through from the stomach to the small bowel very rapidly, which causes the one-hour GTT value to be a lot higher than expected.

So a GTT should have more than just one high value to nail the diagnosis. And, no, the one-hour value doesn't count as "casual" as it occurred after a huge sugar load.

See diagnosis of diabetes for more information.