How accurate is a hemoglobin a1c test in indicating hypoglycemia?

Poor: Hba1c is fair at detecting chronically high bgs, but very poor at detecting low bgs. Fortunately, true low bgs are very rare and almost never sustained or recurrent. The sensation of "hypoglycemia", when related to sugar at all in people not treated with diabetes medications, is usually the normal response to low-ish sugars, which corrects them and keeps the body well.

Not good at all.....: Hgba1c is a spontaneously formed adduct of HGB generated by nucleophilic attack of the n-terminal nh2 of beta globin on the anomeric carbon of glucose. In setting of hyperglycemia, its levels rise, and indeed can be a good indicator of blood glucose levels over the preceding several months. However, as a marker of transient low blood glucose (which is really the only way it happens), it stinks.