Additional Information/Important Notes

Repeat hemoglobin A1c testing or follow-up with an alternative test such as the 2-hour OGTT is required prior to the diagnosis of diabetes.  
 

Prediabetes: Patient counseling and commitment to a course of lifestyle modification is recommended with follow-up testing 3-6 months later.  

Diabetes mellitus: HbA1c correlates highly with average daily glycemia over the preceding 60-90 day period.  While ‘good control’ is generally considered to be HbA1c < 7.0%, individual factors influence HbA1c goals and attained results, which providers should take into account when using HbA1c in patient management and counseling. In particular, HbA1c does not reliably capture frequency and severity of treatment-related hypoglycemia, which may obligate relaxation of HbA1c goals for the patient.”

Note: Any condition that shortens erythrocyte survival or decreases mean erythrocyte age will lower HbA1c results regardless of the assay method. HbA1c results after blood transfusion should be interpreted with caution. The presence of hemoglobin variants can interfere with the measurement of hemoglobin A1c (HbA1c). The advantage of using ion exchange chromatography methods is most variants that would affect HbA1c results can be detected from analysis of the chromatogram so inaccurate results are less likely to be reported.

Conditions that affect red blood cell turnover (hemolytic and other anemias, glucose-6-phosphate dehydrogenase deficiency, recent blood transfusion, use of drugs that stimulate erythropoesis, end-stage kidney disease, and pregnancy) may result in discrepancies between the A1C result and the patient’s true mean glycemia. Hemoglobin variants must be considered, particularly when the A1C result does not correlate with the patient’s SMBG levels. However, most assays in use in the U.S. are accurate in individuals heterozygous for the most common variants (see http://www.ngsp.org/interf.asp). Other measures of average glycemia such as fructosamine and glycated albumin are available, but their translation into average glucose levels and their prognostic significance are not as clear as for A1C.