A1C Reliably Estimates Blood Sugar Levels

Dr. Jessica Moore, ND

  • An A1C test reliably estimates blood sugar levels over the past 80-120 days.
  • Used to either diagnose diabetes or to monitor diabetes treatment.
  • It is a simple and inexpensive blood test that does not require fasting or preparation
  • Alternate names used: HbA1C, glycosylated hemoglobin and glycated hemoglobin

This cornerstone test differs from the blood sugar checks that people do every day. When a person uses a glucometer to check their blood sugar at home, they are taking a snap shot of their blood glucose level in that very moment. This type of real time assessment is labile, meaning it can quickly change after short term variations in a person’s lifestyle and habits including, but not limited to the following: food intake, exercise, stress, acute illness, medications, medication compliance etc. Conversely, an A1C represents an average of the glucose levels over the past 3 months and is not sensitive to the short-term variations listed above.

Our red blood cells (RBCs) contain hemoglobin (Hb), which is responsible for carrying oxygen in our blood. As RBC circulate, glucose is naturally combined with Hb to form glycosylated Hb. This event is large irreversible. The reason and A1C test is reflective of blood sugar control over only the last 3 months is because the life span of a RBC is approximately 100-120 days, or 3 months. The amount of glycosylated Hb is directly correlated with the average amount of glucose present in the blood stream over that time. However, the mean blood glucose within the most recent 30 days contributes to 50% of the result.

A1C can be used to both diagnose diabetes and to monitor treatment. In general, most practitioners use the following reference values to categorize blood sugar control:

  • 0%-5.9%: Non-diabetic adult or child
  • 0%-6.4%: Pre-diabetes
  • >5%: Diagnosis of diabetes
  • <7.0%: Good diabetic control
  • 0%-9.0%: Moderate diabetic control
  • > 9.0%: Poor Diabetic control > 9%

If you are diagnosed with pre-diabetes or diabetes, your A1C goal should be tailored to your age, comorbidities and life expectancy. Once a target A1C value is established for a particular patient with diabetes type II, A1C should be measured every 3 months if they are outside of their goal range and every 6 moths if they are maintaining well within their goal range. Special circumstances such as pregnancy may require more frequent monitoring.

In addition to gaining insight into blood sugar control, studies have suggested that A1C values are also reliably correlated with:

  1. Diabetic microvascular and macrovascular complications
  2. Cardiovascular morbidity and mortality
  3. Total mortality
  4. Cancer risk and cancer-related mortality (especially: liver, pancreas, ovary, colorectum, lung, bladder and breast)

If you have questions or concerns about your blood sugar control or need screening testing, please reach out to me or your other providers at Sage Clinic.


In Good Health,

Dr. Jessica Moore, ND



  1. Overview of medical care in adults with diabetes mellitus(2018). UpToDate.
  2. Atsushi Goto (2015) Hemoglobin A1cLevels and the Risk of Cardiovascular Disease in People Without Known Diabetes. Medicine (Baltimore). 2015 May; 94(17): e785.
  3. Atsushi Goto et al. (2016). High hemoglobin A1c levels within the non‐diabetic range are associated with the risk of all cancers. Int J Cancer. 2016 Apr 1; 138(7): 1741–1753.