From the Guidelines
A low Hemoglobin A1c (HbA1c) level becomes concerning when it falls below 5% in non-diabetic individuals or when it drops too rapidly in diabetic patients on treatment, as indicated by the most recent guidelines from the American College of Physicians in 2018 1. Low HbA1c can indicate hypoglycemia (low blood sugar), which is particularly dangerous in diabetic patients taking insulin or sulfonylureas like glipizide or glyburide. Other causes of abnormally low HbA1c include certain anemias, liver disease, kidney failure, increased red blood cell turnover, hemoglobinopathies, and recent blood loss or transfusions. Some key points to consider when evaluating low HbA1c levels include:
- The American Diabetes Association recommends an A1C goal of <7% for most nonpregnant adults, with more stringent goals (such as <6.5%) for selected individual patients and less stringent goals (such as <8%) for patients with a history of severe hypoglycemia or limited life expectancy 1.
- The American College of Physicians suggests that clinicians should aim for an HbA1c level between 7% and 8% in most patients with type 2 diabetes, as this range is associated with a lower risk of hypoglycemia and other adverse effects of treatment 1. Patients with unexplained low HbA1c should undergo further testing, including:
- Fasting glucose levels
- Complete blood count
- Liver and kidney function tests
- Possibly hemoglobin electrophoresis The concern with low HbA1c stems from its potential to mask underlying health issues or indicate frequent hypoglycemic episodes, which can cause symptoms ranging from confusion and dizziness to seizures and loss of consciousness. In diabetic patients, treatment adjustments may be necessary to prevent dangerous hypoglycemic events, including reducing insulin doses or switching from sulfonylureas to medications with lower hypoglycemia risk like metformin, DPP-4 inhibitors, or GLP-1 receptor agonists, as recommended by the American Diabetes Association 1.
From the Research
Low Hemoglobin A1c (HbA1c) Levels
A low HbA1c level can be concerning in certain situations. The following points highlight when a low HbA1c level may be a cause for concern:
- Hypoglycemia risk: A low HbA1c level, especially if achieved rapidly, may increase the risk of hypoglycemia, particularly in individuals with a history of severe hypoglycemia or those taking insulin or sulfonylureas 2.
- Individualized glycemic goals: The American Diabetes Association recommends individualized glycemic goals, and a low HbA1c level may not always be appropriate for everyone, particularly for those with a high risk of hypoglycemia, limited life expectancy, or extensive comorbidities 3.
- Glucose variability: A low HbA1c level may not always reflect glucose variability, and continuous glucose monitoring (CGM) can provide a more comprehensive picture of glucose control, helping to identify individuals at risk for hypoglycemia 4.
- Treatment considerations: In some cases, a low HbA1c level may not be the primary goal of treatment, and other factors such as weight loss, blood pressure control, and cardiovascular risk reduction may take precedence 5, 6.
Key Considerations
When evaluating a low HbA1c level, the following factors should be considered:
- Baseline HbA1c level: The baseline HbA1c level can influence the achievement of glycemic goals, and a lower baseline HbA1c level may be associated with a higher risk of hypoglycemia 6.
- Treatment regimen: The treatment regimen, including the use of insulin, sulfonylureas, or other medications, can impact the risk of hypoglycemia and the achievement of glycemic goals 2, 3.
- Individual patient characteristics: Individual patient characteristics, such as age, comorbidities, and life expectancy, should be taken into account when evaluating a low HbA1c level and determining the appropriateness of glycemic goals 3, 5.