Is HbA1c a good test for showing IR?

Back on this forum, after a long break. Meanwhile, I've gotten a new doc (to my regrets, I really liked my previous doc). I proposed to him to investigate my possible IR, based at the non-response of the Tx and my glucose data. He said that my glucose data didn't say that much since I had not been sober (i.e. I had eaten when the tests were taken). He proposed to test glycosylated hemoglobin (HbA1c), since "in individuals with poorly controlled diabetes, the quantities of these glycated hemoglobins are much higher than in healthy people". Now, is this the right way to go? The Wikipedia page warns that readings will be lower if red blood cell had a lower life span than normal. Since the past 3 month include about 1 month of Tx time, I wonder if the Tx didn't shorten my red blood cell life span at the time.

And how does the HbA1c relate to the HOMA test?