22/05/2026
HBA1C IS A LIE. YOU HAVE BEEN MEASURING THE WRONG THING.
Averages lie. HBA1c is an average.
That perfect 7.0% is hiding dangerous lows and deadly highs. Time in range is the real metric. Most people don’t know this.
HbA1c measures your patient's average glucose over the past three months. That is all it does. It does not tell you about the extremes. It does not tell you about variability. It does not tell you about the dangerous lows or the toxic highs.
Here is a simple example:
Patient A has glucose of 150 mg/dL all day, every day. Their HbA1c is 7.0%.
Patient B has glucose of 50 mg/dL for four hours, 300 mg/dL for six hours, and 150 mg/dL for the rest of the day. Their HbA1c is also 7.0%.
Same number. Completely different patients. One is stable. One is a ticking time bomb.
Which one are you treating with that 7.0%? You do not know. Because you only measured the average. And the average told you nothing.
The guidelines changed. Most of you did not notice.
The International Consensus on Time-in-Range was published in 2019. That is seven years ago. It recommended time-in-range (TIR) as the preferred metric for assessing glycemic control when continuous glucose monitoring (CGM) is available.
The American Diabetes Association now states that TIR is "strongly associated with the risk of microvascular complications" and should be used alongside HbA1c.
The European Association for the Study of Diabetes says the same.
But Most people are still writing "HbA1c 7.0%, good control" in their notes and moving on. No CGM. No TIR. No questions about time spent low or high. That is not a resource problem. That is a knowledge problem.
What time in range actually tells you:
TIR is the percentage of time a patient's glucose stays between 70 and 180 mg/dL.
A TIR above 70 percent means excellent control. Between 50 and 70 percent means moderate control that needs improvement. Below 50 percent means poor control and high risk.
But the real power of TIR is what it reveals about extremes.
Time below range (TBR) is time spent with glucose below 70 mg/dL. Every minute below 70 increases risk of hypoglycemia unawareness, falls, seizures, and death. A patient with 4 percent TBR has clinically significant hypoglycemia.
Time above range (TAR) is time spent with glucose above 180 mg/dL. Every minute above 180 increases risk of retinopathy, nephropathy, and neuropathy. A patient with 25 percent TAR is accumulating damage.
HbA1c tells you none of this. A 7.0% HbA1c could come from a patient with 2 percent TBR and 20 percent TAR or a patient with 0 percent TBR and 10 percent TAR. Same number. Completely different risk profile.
You cannot manage what you do not measure.
What you need to do starting tomorrow:
One: Stop celebrating the number without knowing the story behind it.
When you see an HbA1c of 7.0%, ask: what is the time in range? What is the time below range? What is the time above range? If you do not know, you do not know if your patient is safe.
Two: Learn to read GCM data. GCM is Continuous Glucose Monitoring (CGM), a sensor that tracks glucose 24/7.
If your patient has a CGM, you have no excuse. Learn the metrics. Learn the ambulatory glucose profile. Learn to spot patterns. It takes one hour. One hour to stop practicing 1990s medicine.
Three: For patients without CGM, change your questions.
Stop asking "what is your blood sugar?" Start asking "when was your last low?" "How often do you feel dizzy or shaky?" "Do you ever wake up with night sweats?" "Do you ever check and find yourself over 300?" These questions reveal what HbA1c hides.
Four: Stop using HbA1c alone to make treatment decisions.
If you are adjusting insulin or oral medications based only on HbA1c, you are flying blind. You do not know if you are fixing highs while causing dangerous lows. That is not medicine. That is gambling.
I am not saying throw away HbA1c. It has value. It correlates with outcomes. It is cheap. It is available everywhere.
But I am saying this: relying on HbA1c alone in 2026 is like relying on a rearview mirror to drive forward. It tells you where you have been. It does not tell you about the cliff ahead.
Time in range tells you about the cliff. It tells you about the lows that will cause a seizure. It tells you about the highs that will destroy a kidney. It tells you what HbA1c hides.
If you are not using TIR, you are not practicing modern diabetes care. That is not an insult. That is an observation. The question is what you do with it.
Update your practice. Learn the metrics. Ask better questions.
