A1C vesus serum glucose

My father’s A1C is 6.0 on his last test blood test.  This seems to be a pretty good value.  However, his serum glucose during the day is not so great.

My understanding is that every time your sugar spikes, your hemoglobin becomes glycoslated.  Thus, A1C is a reflection of how often and how much your sugar spikes.  At least that is my understanding.  Dad’s daily serum glucose numbers are high yet his A1C has decreased.  This is causing me to wonder if there are situations where A1C is not a good reflection of someone’s glucose control.  Is it possible that if someone has drastic swings in serum glucose to have a fairly good A1C because their glucose spikes are often set with glucose lows?  So in other words, say you have two patients each of them take their glucose every hour for 24 hours every day for 90 days.  Both patients have an average 24-hour glucose of 110 over the 90 day period.  However, Patient A has highs of 170 and lows of 50 and Patient B has highs of 130 and lows of 90.  Again both average out to 110.  Would you expect Patient A to have a higher A1C than Patient B because Patient A has higher spikes (i.e., 170)?  Or, would you expect Patient A and B to have about the same A1C because they average the same – 110.

[Lee Kirksey, MD]

Hello
I would guess that the spikes are short lived and transient and that if you plotted the glucose level over a 24 cycle, you would find that his levels are well controlled much more often than not. Importantly however, it is the wide swings in blood glucose which cause people to feel ill. They can also be quite dangerous. Talk to his doctor about adjusting his meds to obtain a more even course
Best of luck