From the Guidelines
To diagnose diabetes after finding an HbA1c of 7%, a repeat HbA1c test should be performed to confirm the diagnosis, unless there are already clear symptoms of diabetes present. An HbA1c of 7% is above the diagnostic threshold of 6.5% for diabetes, but confirmation is standard practice, as stated in the 2021 standards of medical care in diabetes 1. Alternative confirmatory tests include a fasting plasma glucose test (diabetes is diagnosed if ≥126 mg/dL) or a 2-hour plasma glucose test during an oral glucose tolerance test (diabetes is diagnosed if ≥200 mg/dL), according to the executive summary of the 2012 standards of medical care in diabetes 1.
Some key points to consider when confirming the diagnosis include:
- The test should be performed in a laboratory using a method that is National Glycohemoglobin Standardization Program (NGSP)-certified and standardized to the Diabetes Control and Complications Trial (DCCT) assay 1
- Fasting is defined as no caloric intake for at least 8 h for the fasting plasma glucose test 1
- The oral glucose tolerance test should be performed as described by the World Health Organization, using a glucose load containing the equivalent of 75 g anhydrous glucose dissolved in water 1
Once diabetes is confirmed, a comprehensive evaluation should be conducted, including:
- Assessment of cardiovascular risk factors
- Screening for complications (eye exam, foot exam, kidney function tests)
- Diabetes education The elevated HbA1c indicates that average blood glucose levels have been around 154 mg/dL over the past 2-3 months, suggesting chronic hyperglycemia, which is associated with increased risk of microvascular complications like retinopathy, nephropathy, and neuropathy, as noted in the 2021 standards of medical care in diabetes 1.
From the Research
HbA1c 7: Follow-up to Diagnose Diabetes
- An HbA1c level of 7 is above the normal range, indicating impaired glucose regulation or diabetes 2, 3, 4.
- According to the International Expert Committee, a diagnosis of diabetes can be made if the HbA1c level is 6.5% or greater, confirmed with a repeat HbA1c test 3.
- However, an HbA1c level of 7 may require further testing to confirm the diagnosis, such as fasting plasma glucose or oral glucose tolerance tests 3, 4.
- The American Diabetes Association recommends screening for type 2 diabetes annually in patients 45 years and older, or in patients younger than 45 years with major risk factors 4.
- Additional testing to determine the etiology of diabetes is not routinely recommended, but may be necessary in some cases 4.
Diagnostic Criteria for Diabetes
- Fasting plasma glucose level of 126 mg/dL or greater 4
- A1C level of 6.5% or greater 3, 4
- Random plasma glucose level of 200 mg/dL or greater 4
- 75-g two-hour oral glucose tolerance test with a plasma glucose level of 200 mg/dL or greater 4
Comparison of HbA1c with Other Diagnostic Tests
- HbA1c has been shown to be a more sensitive test compared to fasting plasma glucose in the diagnosis of diabetes 5.
- However, the sensitivity and specificity of HbA1c can vary depending on the population and ethnicity being tested 5, 6.
- The compatibility of HbA1c with oral glucose tolerance test and fasting plasma glucose has been evaluated, and the results suggest that HbA1c can be a useful diagnostic tool, but may not be suitable for all populations 5.