The A1C test provides a valuable snapshot of a person’s average blood sugar control, but a high result does not automatically equate to a diagnosis of diabetes. This measurement, also known as glycated hemoglobin or HbA1c, reflects the percentage of hemoglobin—a protein inside red blood cells—that has sugar attached to it, a process called glycation. Since red blood cells typically live for about two to three months, the test offers a weighted average of blood glucose levels over that period, giving a long-term view useful for screening and monitoring. While the primary use of the A1C test is for assessing diabetes risk, various non-diabetic factors can genuinely elevate this reading, leading to confusion about the underlying cause. Understanding these nuances is necessary for accurately interpreting a high A1C result.
Defining the A1C Ranges
The American Diabetes Association (ADA) establishes standard numerical thresholds for interpreting A1C results to classify metabolic status. An A1C result below 5.7% is considered normal, indicating healthy long-term glucose control. When the percentage falls between 5.7% and 6.4%, it is classified as prediabetes, signaling that blood sugar levels are higher than normal but not yet high enough to meet the diagnostic criteria for full diabetes.
A reading of 6.5% or higher, when confirmed by a second test, is the standard cutoff used to diagnose diabetes. A result in the prediabetes range is still considered high, placing the individual at an increased risk for developing type 2 diabetes and cardiovascular disease. Even without diabetes, an elevated A1C indicates a need for medical attention and lifestyle adjustments to prevent future complications.
Medical Conditions That Elevate A1C Without Diabetes
Certain underlying health conditions can cause a true elevation in A1C by altering the natural physiology of red blood cells or affecting glucose metabolism through non-diabetic means.
Anemia and Red Blood Cell Lifespan
One significant factor is iron deficiency anemia, which causes red blood cells to live longer than their typical 120-day lifespan. This extended survival time exposes the hemoglobin to blood glucose for a greater duration, allowing more sugar to attach. This leads to a genuinely higher A1C percentage that overstates the true average glucose level.
Kidney and Liver Disease
Chronic kidney disease, particularly when advanced, can also contribute to an elevated A1C through a mechanism called metabolic acidosis. The buildup of acids in the body speeds up the rate at which glucose binds to the hemoglobin protein, causing the A1C result to appear higher than the actual average blood sugar concentration. Furthermore, severe liver disease or chronic alcoholism can alter both red blood cell turnover and the body’s ability to clear glucose, resulting in unexpected A1C values.
Endocrine Disorders
Specific endocrine disorders, such as Cushing’s syndrome, lead to an overproduction of cortisol, a stress hormone that naturally raises blood glucose levels. This sustained, non-diabetic form of hyperglycemia causes a true increase in the amount of glycated hemoglobin, reflecting a physiological elevation of blood sugar secondary to the hormonal imbalance. These conditions require a thorough medical workup to distinguish them from primary type 2 diabetes.
When the Test Results Are Not Accurate
Beyond conditions that cause a true elevation, other factors can interfere with the laboratory measurement itself, leading to a result that is falsely high or falsely low.
Hemoglobinopathies
Genetic variations in hemoglobin structure, known as hemoglobinopathies, are a major source of interference, most commonly seen in people with traits like sickle cell or thalassemia. These structural differences in the hemoglobin molecule can disrupt the specific chemical assay used by the lab, causing the A1C value to be incorrectly reported.
Rapid Cell Turnover
Conditions that cause rapid red blood cell turnover, such as hemolytic anemia or recent severe blood loss, typically result in a falsely low A1C reading. This occurs because the red blood cells do not survive long enough to accumulate the full two-to-three months’ worth of glucose. Conversely, a recent blood transfusion can also skew results significantly, as the patient’s blood contains new red blood cells with a very low glycation level, diluting the overall measurement.
Medications
Certain medications can also interfere with the test or affect blood cell dynamics. High-dose aspirin, chronic opioid use, or some treatments for HIV and hepatitis have been reported to interfere with the A1C assay, sometimes causing a falsely elevated result. When A1C results are inconsistent with a person’s daily glucose measurements or clinical picture, healthcare providers must consider the possibility of a testing interference rather than a true metabolic problem.
Next Steps After a High Reading
Receiving a surprisingly high A1C result necessitates a consultation with a healthcare provider to determine the underlying cause, whether it is a true metabolic change or a testing inaccuracy. The physician will often order follow-up tests to confirm the result and rule out interference.
These secondary tests frequently include a Fasting Plasma Glucose test, which measures blood sugar after an eight-hour fast, or an Oral Glucose Tolerance Test (OGTT), which tracks the body’s response to a standardized sugar load. If a hemoglobinopathy or other interference is suspected, alternative markers of long-term glucose control, such as fructosamine or glycated albumin, may be ordered, as these tests are not dependent on red blood cell lifespan.
A high A1C warrants proactive steps, especially if it falls in the prediabetes range. Implementing lifestyle changes, including increasing physical activity and adopting a diet higher in fiber and complex carbohydrates, can significantly help manage and lower blood sugar levels. Communication with a medical team is necessary to interpret the findings and create a personalized plan to mitigate the risks associated with prolonged glucose elevation.