22% of US Adults With Diabetes Don't Know Their A1c Level

Marlene Busko, for Medscape

June 05, 2023

The study covered in this summary was published on medRxiv as a preprint and has not yet been peer reviewed.

Key Takeaways

  • 22% of US adults reported not knowing their current A1c value when they participated in a recent National Health and Nutrition Examination Survey (NHANES) assessment. They had been diagnosed with diabetes and had undergone an A1c blood test during the prior year.

  • Sociodemographic characteristics associated with not knowing one's A1c values were having a lower income or less education and not being non-Hispanic White.

  • Among participants who said they knew their most recent A1c value, 48% reported an A1c that differed by >0.5% compared with a lab-measured A1c at the time of the survey.

Why This Matters

  • Long-term poor glycemic control is associated with increased risk of neuropathy, nephropathy, retinopathy, and ketoacidosis in diabetes and increased risk of cardiovascular events in type 2 diabetes.

  • Patients' knowledge and understanding of A1C are essential for diabetes self-management.

  • Results from recent studies have indicated that patients with better knowledge of their A1c level experience better overall care and diabetes management, and they have better knowledge of medication, better adherence, and increased treatment satisfaction.

  • The findings suggest that clinicians should evaluate and, if needed, enhance patients' knowledge of their A1c.

  • The findings reinforce the need for improved communication between adults with diabetes and their healthcare providers. Assessing how A1C results are communicated and improving patients' knowledge and understanding of A1C should be priorities for providers to maximize diabetes self-management and to mitigate the long-term negative consequences of poor glycemic control.

Study Design

  • The researchers identified 2723 people aged at least 20 years who participated in any one of three consecutive NHANES assessments from 2013 to 2020 and who reported receiving a diabetes diagnosis with a laboratory-measured A1C value. The study excluded those who declined to provide a self-reported A1C value.

  • The NHANES-associated physical examination included collection of fasting blood samples followed by A1c measurement. The study authors defined A1C concordance as a difference of ≤0.5% between self-reported and lab-measured A1c values. They defined discordance as a >0.5% difference between the self-reported values and the lab-measured values.

Key Results

  • Most participants (61%) were non-Hispanic White, and 54% were men. The average age was 60 years; the mean self-reported A1c value was 7.2%; and the mean lab-measured A1c value was 7.4%.

  • 9% did not know the A1c target that was set by their usual healthcare provider.

  • 22% of participants who self-reported a diabetes diagnosis did not know their most recent A1c value.

  • A1c ignorance was less common among those who were non-Hispanic White and was more common among those with lower income, less formal education, and those who did not know or did not have a target A1c value set by their healthcare provider

  • There were no statistically significant associations between those who knew and those who did not know their A1c values and age, sex, and insurance status.


  • The study sample included a relatively small number of people with diabetes.

  • The data did not differentiate between type 1 and type 2 diabetes.

  • The results cannot be generalized to patients with undiagnosed diabetes.

  • The moderate concordance between self-reported and lab-measured A1c values could be due to changes in glycemic control since the last A1c test rather than inaccurate self-reporting.

  • Since the data were self-reported, social desirability bias may have caused underreporting of high A1c values.

  • Since NHANES provides cross-sectional data, this study cannot determine cause and effect.


  • The study did not receive any specific funding from any source.

  • None of the authors had relevant financial disclosures.

This is a summary of a preprint research study, "Discordance Between Self-reported and Lab-Measured A1c Among US Adults With Diabetes: Findings From the National Health and Nutrition Examination Survey (2013–2020)," written by researchers from the University of Pittsburgh, Pittsburgh, Pennsylvania, published on medRxiv, and provided to you by Medscape. This study has not yet been peer reviewed. The full text of the study can be found on medRxiv.com.

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