From the Guidelines
Hemoglobin A1c (HbA1c) is a blood test that measures average blood sugar levels over approximately 2-3 months, reflecting average glycemia and having strong predictive value for diabetes complications 1.
What is HbA1c?
HbA1c is a crucial tool for assessing glycemic status in both clinical practice and clinical trials. It works by showing the percentage of hemoglobin proteins that have glucose attached to them.
- Normal HbA1c levels are below 5.7%,
- 5.7-6.4% indicates prediabetes,
- and 6.5% or higher suggests diabetes.
Importance of HbA1c Testing
This test is valuable because it provides a longer-term picture of blood sugar control compared to daily glucose readings, which only show levels at a specific moment.
- For people with diabetes, doctors typically recommend maintaining HbA1c below 7%, though targets may vary based on individual health factors 1.
- The test should be performed every 3 months for people with diabetes, or twice per year for those with stable glycemia within goal 1.
How HbA1c Works
HbA1c works because red blood cells live for about 120 days, and during this time, glucose in the bloodstream naturally attaches to hemoglobin.
- Higher blood sugar levels cause more glucose to attach, resulting in higher HbA1c percentages, reflecting average glucose control over the lifespan of these cells.
Clinical Recommendations
The American Diabetes Association recommends HbA1c testing at least twice per year in patients who are meeting treatment goals and quarterly in those whose therapy has changed or who are not meeting glycemic goals 1.
- Point-of-care testing for HbA1c allows more timely treatment changes 1.
- Avoiding hypoglycemia should always take precedence over achieving HbA1c targets 1.
From the Research
Definition and Purpose of Hemoglobin A1c (HbA1c)
- Hemoglobin A1c (HbA1c) is a widely used tool for diagnosing, screening, and managing patients with diabetes 2.
- It is an important indicator of long-term glycemic control, reflecting the cumulative glycemic history of the preceding two to three months 3.
- HbA1c is used to assess glycemic control in people with diabetes and has been accepted as an index of glycemic control since the mid-1970s 4.
Clinical Use and Interpretation of HbA1c
- HbA1c is a reliable measure of chronic hyperglycemia and correlates well with the risk of long-term diabetes complications 3.
- The American Diabetes Association has recommended glycated hemoglobin (HbA1c) as a possible substitute to fasting blood glucose for diagnosis of diabetes 3.
- HbA1c measurement can be subject to confounders and effect modifiers, particularly in the setting of hematologic abnormalities 4, 5.
- It is recommended to measure HbA1c every 3-6 months, and treat to a target level of < 7% to reduce long-term complications, especially microvascular complications 6.
Relationship between HbA1c and Cardiovascular Risk
- Elevated HbA1c has been regarded as an independent risk factor for coronary heart disease and stroke in subjects with or without diabetes 3.
- Results from large clinical trials support the modern perspective that the HbA1c target should be personalized according to the risks and benefits of glycemic control, especially in patients with diabetes and elevated cardiovascular risk 2.