Davis's Lab & Diagnostic Tests
Hemoglobin A₁c
General
Core Lab Study
Synonym/Acronym:
A1c, glycated hemoglobin (Hgb), glycohemoglobin.
Rationale
To identify individuals with diabetes and to monitor treatment in individuals with diabetes by evaluating their long-term glycemic management.
A small group of studies in this manual have been identified as Core Lab Studies. The designation is meant to assist the reader in sorting the basic “always need to know” laboratory studies from the hundreds of other valuable studies found in the manual—a way to begin putting it all together.
Normal, abnormal, or various combinations of core lab study results can indicate that all is well, reveal a problem that requires further investigation with additional testing, signal a positive response to treatment, or suggest that the health status is as expected for the associated situation and time frame.
Hemoglobin A1c is mainly used to screen and assess for diabetes.
Patient Preparation
There are no food, fluid, activity, or medication restrictions unless by medical direction.
Normal Findings
Method: Capillary electrophoresis
| Normal (without diabetes) | 4.8%–5.6% |
| Prediabetes | 5.7%–6.4% |
| Values above the range for prediabetes indicate diabetes | Greater than or equal to 6.5% |
Values vary widely by method. The recommended treatment goal assumes the use of a standardized test, as referenced to the National Glycohemoglobin Standardization Program—Diabetes Control and Complications Trial, and the absence of clinical conditions such as hemoglobinopathies, anemias, and kidney and liver diseases known to affect the accuracy of the test results.
| Recommended Goals for Monitoring Glycemic Management Using Hgb A1c | A1c% | ||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Children and adolescents (applicable to all ages in the pediatric category; however, goals should be individualized especially for type 1 diabetes, and special consideration should be given to age-related lack of awareness for hypoglycemia when setting less stringent goals) | Less than 7% | ||||||||||||||||||||||||||||||||||||||||
| Pregnant females (goals are stricter for pregnant females, especially in the second and third trimesters, related to hemodilution and increased red blood cell [RBC] turnover which has the effect of independently decreasing A1c) | 6%–6.5%; the goal may be relaxed to 7% in order to avoid hypoglycemia | ||||||||||||||||||||||||||||||||||||||||
| Nonpregnant adults with or without diabetes who do not experience significant hypoglycemia (see table note) | Less than 7% | ||||||||||||||||||||||||||||||||||||||||
| Nonpregnant adults with or without diabetes who do not experience significant hypoglycemia: Using data provided from the Ambulatory Glucose Profile, the goal parallel to less than or equal to 7% | Time in range greater than 70% with time below range less than 4% | ||||||||||||||||||||||||||||||||||||||||
| Older adults who are otherwise healthy with good cognitive function and few chronic health issues | Less than 7%–7.5% | ||||||||||||||||||||||||||||||||||||||||
| Diabetes (stricter goals are reasonably recommended for certain individuals with diabetes, e.g., those who are otherwise healthy, are newly diagnosed, are type 2 diabetics being treated with lifestyle adjustments and limited oral antidiabetes medications such as metformin to lower glucose levels, have not yet developed complications related to diabetes, do not experience significant hypoglycemia) | 6.5% or less | ||||||||||||||||||||||||||||||||||||||||
| Diabetes (less strict goals are reasonably recommended for certain individuals with diabetes, e.g., older adults; those who have been diagnosed with diabetes for a lengthy period of time and have been unsuccessful achieving lower A1c goals; have complications related to diabetes; have one or more comorbidities; have a short life expectancy; are being treated with multiple antidiabetes medications, including insulin, to lower glucose levels; have a documented history of hypoglycemia) | Less than 8% | ||||||||||||||||||||||||||||||||||||||||
| Age, blood loss (significant), erythropoietin therapy, ethnicity, hemodialysis, hemoglobinopathies, HIV treatment, pregnancy, and recent blood transfusion are some of the variables that independently affect blood glucose levels, thereby also affecting A1c levels and the approach to glycemic management. A1c goals for persons with diabetes are set and monitored by the health‑care provider (HCP) in collaboration with the patient. Goals are based on a variety of factors that include the number of years diagnosed with diabetes, identification of complications related to diabetes, identification of comorbidities, evidence of hypoglycemia, life expectancy based on risk factors, recommended therapies, ability to access resources required to support the treatment plan, level of available and dependable support (e.g., for pediatric patients, patients with language barriers, or patients with intellectual, emotional, or physical impairments).Summarized from American Diabetes Association. Standards of Medical Care in Diabetes. (2022). Diabetes Care, 45(Suppl. 1):S83-S96. | |||||||||||||||||||||||||||||||||||||||||
Critical Findings and Potential Interventions
N/A
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