Is There a Perfect A1c?
If you were to get your lab results and see an A1c of 6.5%, how would that make you feel? Ecstatic? Frustrated? Reactions would run the gamut based on many factors, including personal experiences and discussions with your physician and peers. This is understandable given that, even if following the American Diabetes Association (ADA) or other professional society guidelines, there has not been a clear consensus on the perfect A1c. Over the years, recommendations have fluctuated with the move now away from one set number, such as less than 7%, and towards a spectrum looking at each person individually. Even when the guidelines were more rigid, recommended A1c goals have been stated with “less than” phrasing without a specific guide on the bottom number of the goal range.
A1c Limitations
When using the A1c level, there are several points to consider. We now recognize the limitations of an A1c including inaccuracies based on health factors such as anemia and kidney disease. In addition, A1c can differ by a few tenths of a point from one lab draw to the next on the same day with no other change. When talking about tight control, this means that with an A1c of 6.3 vs 6.6%, there could actually be no significant difference at all, but cause unnecessary distress.
Balancing the Risk of Complications
The A1c targets set by the ADA and professional societies are based on literature and randomized control trials looking at complications from hyperglycemia and hypoglycemia. Hypoglycemia can clearly lead to immediate dangerous events such as loss of consciousness and seizure. The data on hyperglycemia points to an increased risk for microvascular complications such as retinopathy and nephropathy with long-term elevated blood glucose. These studies show that lower A1c percentages are associated with fewer microvascular complications over time but an increased risk of short-term adverse events from hypoglycemia. Striking the perfect balance is the ultimate goal.
In general, the common recommendation to achieve the optimal A1c is to maintain as low a level as possible while avoiding hypoglycemia. Simple to say, but what that looks like for each person and at different times in life varies.
Age Considerations
Age plays a role in blood glucose management. At a certain point, the time to develop adverse effects from hyperglycemia may be small enough so that the risks are not as significant. Combine this with the likelihood of blunted autonomic responses to severe lows as we age, and the risk of hypoglycemia increases. In this case, a higher A1c target may be appropriate.
Life Circumstances
What else is going on in your life? If you have just started a high-stress job or have been dealing with mental health issues, a pristine glucose report may not be possible or even what is best for overall quality of life. Diabetes distress and burnout are significant complications of diabetes as well, and should be considered along with microvascular and macrovascular complications.
CGM and Time in Range
Increased widespread use of continuous glucose monitors (CGM), produces more detailed reports that can be analyzed and used to assess glucose management. The time in range metric is used to track the amount of time spent in the blood glucose target range of 70-180 mg/dL, essentially outside of hypoglycemia and hyperglycemia. Professional societies do provide more specific guidance on hypoglycemia and calculated risk balance when using CGM. In general, the consensus is <4% of time should be spent in a glucose range of less than 70 mg/dL and <1% of time spent below 54 mg/dL. However, older/high-risk individuals are separated out with a recommendation for more strict avoidance of hypoglycemia with a goal of <1% time spent below 70mg/dL. Pregnancy-specific ranges are also separated out based on unique goals during that time.
It should be noted that 1% represents 15 minutes. For example, if someone has time below range of 4%, it means they are below 70 mg/dL for one hour per day on average.
Conclusion
In addition to a preference for using more detailed and informative monitoring with CGMs, currently the proposal for target A1c is that one size does not fit all. Personalized targets are now the standard. So, is lower better when it comes to A1c? Maybe – if you have the tools, time, and ability to also avoid significant low blood glucose. If you wear a CGM and can track and treat hypoglycemia early and effectively, and your A1c is 5.8, then likely this is all great news. If, for example, you do not wear a CGM, have hypoglycemia unawareness, or have other health factors that make hypoglycemia more risky and your A1c is 7.3 then this may also be great. And remember to balance strict blood glucose management with your mental health, life events, and overall quality of life.
Additional Resources:
Which Is Better…a Lab A1c Test or the Estimated A1c (GMI) from a CGM?
5 Ways to Turn Your A1c Into Action
A Dose of Dr. E: Why the A1c Sucks (And Why Time in Range Is More Important)
Interesting, but the problem with CGM Time in Range reports is that many sensors have proven faulty, which in turn means these percentages are false; my Freestyle Libre 2 sensors under read by 30-60+% on many an occasion, and since I won’t remove it until testing for another day or 2 to ensure it is indeed faulty, the erroneous figures remain on the reader, which in turn I and my endo download for our records.
You are very correct. If the CGM is reading falsely low or high, it will make the TIR inaccurate. Your experience is not that uncommon.
I have T1D for 55 years without any complications. My A1C is between 5.6 and 6.3 for many years. I have lots of lows due to exercises and low carb foods. My type 1 diabetes specialist said that my A1C should be over 6.0. Screw him since I do not want any complications in the near future.
Congrats on your lack of complications. Your doctors are worried about the lows. You might try one of the hybrid closed-loop systems like the Tandem Control IQ or the Omnipod 5 that will work to keep your lows at a minimum. Any A1c below 7.0 is extremely good.
I am T! for 42ys and struggled with low blood sugars, my medical team and I are trying to prevent the lows. I am 69ys old no other conditions. With the Dexcom CGM I am now 1-2pc low and 1pc high now my AIC is 6.9 not 5.8 . it has been determined by studies that low blood sugars can bring on early dementor and maybe lead to severe brain function loss as we get older.
As much as we try it will never be perfect but now we do have control it just means no days off or time off
Linda…you should get a hybrid closed-loop system such as the Tandem Control IQ or the Omnipod 5. It will really help keep you out of the low ranges.