The reason we choose to make use of A1C What values are suggested, and what impact does it have on A1C, anything from vitamin deficiencies to anemia
Hemoglobin A1C (“HbA1c” or “A1c”) is the most commonly used method for assessing blood sugar levels in people with diabetes. A1C measures blood sugar for two to three months, and in studies such as DCCT or UKPDS, higher A1C amounts are associated with the possibility of complications from diabetes (kidney and nerve diseases). Every one percent decrease in A1C provides substantial protection against these complications.
However, as is typical over some time, A1C cannot capture critical data such as the amount of time in the target range (70-180 mg/dl) and the lower threshold (less than 70 mg/dl).
This article discusses why A1C is used in the first instance and the variables that can cause misleadingly low or high values. In a follow-up piece, we will look at time-in-range and blood sugar variation and methods to quantify and analyze them.
What's A1C, and why is it used?
A1C measures a person's typical blood sugar levels over a 2—to 3-month period. It's one indicator of whether blood glucose levels are managed and is a sign of diabetes management.
Although A1Cs don't provide daily data, lower A1Cs are associated with a lower risk from “microvascular” complications like kidney problems (nephropathy), loss of vision (retinopathy), and damage to nerves (neuropathy). In the same way, higher A1Cs could lead to “macrovascular” complications like heart disease.
A1C can be determined in a laboratory using routine blood tests or the countertop machine found in a doctor's office (and certain pharmacies) with a fingerstick.
A1C determines the percent of “glycated hemoglobin,” a term used to describe hemoglobin, a red blood cell with sugar attached to it. If a person consistently has more blood sugar levels, A1C levels rise because more red blood cells have been covered with sugar. The test represents an average of between 2 and 3 months since once a red blood cell is coated with sugar, the bond becomes irreparably. It's only when the red blood cells are “recycled” (which occurs at intervals of 2 and 3 months) that the sugar coating is removed.
What is “normal” A1C levels for people who do not have diabetes?
Generally speaking, typically, high A1C values suggest an elevated blood sugar level and indicate that a person may be at risk of or be suffering from diabetes. It is the American Diabetes Association (ADA) has defined the following guidelines for determining cutoffs:
A1C < 5.7%
- Average (minimal Risk for Type 2 Diabetes)
- The average blood glucose level in the last 2 to 3 months is within the same range as that of someone without diabetes.
A1C Between 5.7% to 6.4%
- “Prediabetes,” meaning at risk for developing type 2 diabetes
- The levels of blood sugar are higher than usual but not enough to warrant being classified as type 2 diabetes.
A1C > 6.5%
- Diagnosed diabetes
- The average blood glucose level in the last 2 months is within the range of a person with type 2 diabetes.
It is essential to get regular A1C tests, particularly when you suspect you could be at risk for developing diabetes.
What is the A1C objective for people who have been diagnosed with diabetes?
A1Cs of less than 6.5 percent or 7 percent are the ideal goal for most people with diabetes. As each individual with diabetes is different, doctors are advised to establish individual goals for A1C. For instance, the goals could vary based on age and other health issues.
What is the impact of age on A1C?
A1C measures diabetes management; therefore, the A1C of your blood won't change when you age. However, as you get older, your methods of managing diabetes and goals can change. For example, younger people might be more concerned with preventing long-term health problems, while older individuals may be focused on avoiding extreme lows. Consult your physician to determine how age affects your blood A1C levels.
Where are A1C in error or possibly inaccurate?
A lot of progress has been made in establishing a standard and increasing the quality of the A1C test, thanks to the National Glycohemoglobin Standardization Program (NGSP). Test results from non-NGSP-certified laboratories might need to be more accurate. In the machine used and the lab, one A1C test may have a 0.5 percent error margin, which means that the “true” value could be 0.5 percent higher or less than the actual A1C. For instance, if the lab report indicates an A1C number of 7.0 percent, it could be 7.0%. The actual A1C value could range between 6.5 percent to 7.5 percent.
A1C is calculated based on the person's red blood cell turnover (the period of the red blood cell) and the amount of sugar attached to each cell. Certain conditions, like hemoglobin variations, kidney disease, certain types of anemia, and various supplements and drugs, can affect red blood cell turnover and cause inaccurate A1C numbers. Click here to navigate to a list of the factors that affect A1C.
The relationship between A1C values and average blood sugar levels may differ for different people. When studies use continuously monitored glucose (CGM), which is continuous, 24-hour blood sugar levels are evaluated against a measured A1C. The results show a wide range of people. For example, an 8.8% A1C in one person may indicate an average blood glucose reading of 140 mg/dl; in another, it may be as high as 220 mg/dl. This is due to the personal differences in how blood sugars can bind the life span of red blood cells.
A1C to Blood Sugar Conversion
- A1C = 5: 80 mg/dl (4.7 mmol/L)
- A1C = 6: 115 mg/dl (6.3 mmol/L)
- A1C = 7: 150 mg/dl (8.2 mmol/L)
- A1C = 8: 180 mg/dl (10 mmol/L)
- A1C = 9: 215 mg/dl (11.9 mmol/L)
- A1C = 10: 250 mg/dl (13.7 mmol/L)
- A1C = 11: 280 mg/dl (15.6 mmol/L)
- A1C = 12: 315 mg/dl (17.4 mmol/L)
- A1C = 13: 350 mg/dl (19.3 mmol/L)
- A1C = 14: 380 mg/dl (21.1 mmol/L)
CGM is a better method for analyzing a person's glucose levels. It can determine the glucose levels on average, the time within range, and the time under limits. Read more in our earlier article on the beyond of A1C piece here.
Which tools will be there if the A1C test isn't inaccurate or insufficient?
Apart from A1C tests, The most commonly used measures of blood sugar are oral glucose tolerance test (OGTT), CGM, and self-monitored tests for blood glucose.
The OGTT is a diagnostic tool for prediabetes and diabetes, which measures a person's response to consuming a specific volume of sugar. After drinking the sugar beverage, the glucose levels in the blood are checked 2 hours later. Anything below 140 mg/dl is deemed “normal,” between 140 mg/dl to 200 mg/dl points in prediabetes and impaired tolerance to glucose and over 200 mg/dl could indicate the presence of diabetes. It's not ideal to monitor diabetes treatment.
For people with well-established diabetes, CGM has the advantage of continuously tracking blood sugar levels throughout the day (every five to 15 minutes) and providing more precise information about the time range of low blood sugars and excessive blood sugars.
If CGM isn't available using frequent fingersticks, the blood glucose meter at waking, before and after meals, and before bedtime could show when blood sugar levels are high or low and maintain their normal range.
What is essential to keep in mind regarding A1C?
If you have diabetes, it's crucial to understand that A1C isn't an official “grade” for managing diabetes. It's a valuable measure that you and your healthcare professionals can utilize to help guide your decisions and determine the likelihood of developing complications.
Non-glycemic variables that could influence A1C
Although many unobserved elements could affect A1C, the information below does not intend to discredit this test. Knowing how specific circumstances and conditions can affect A1C levels is essential to using A1C as a primary measure for managing diabetes.
Many ailments that impact A1C results are caused by changes in the production of red blood cells and, consequently, the types of anemia. Treatment for anemia may also affect the results of A1C.
Anemia that is not treated
Anemia that is not treated may be due to iron or vitamin B-12 deficiency. Anemia that is not treated can falsely raise A1C levels due to the lower production of blood red cells. You should consult your physician about an entire blood count (CBC) test to determine if you have anemia.
Asplenia (decreased the function of the spleen)
The spleen removes and produces red blood cells. A decreased function could result from surgical removal, congenital diseases, and other blood diseases, such as sickle cell disease. This could result in misleadingly high A1C levels. Asplenia is diagnosed through MRI or echocardiogram, chest radiograph, or examination for screening.
Transfusions of blood and loss of blood
The body's reaction to recent blood loss (creating more giant blood cells) or a blood transfusion could cause a falsely low A1C. However, the following A1C test should show more accurate results. Tell your healthcare professional whether you've recently had a blood transfusion.
A liver condition called cirrhosis
Cirrhosis refers to persistent liver damage that can lead to scarring. It can also impact response to diabetes-lowering drugs such as insulin and cause falsely low A1C levels. Talk to your healthcare professional about a liver test.
Hemoglobinopathy and Thalassemia
Abnormal hemoglobin levels characterize hemoglobinopathy, and Thalassemia is a lower production of functional hemoglobin. Based on the form, that is abnormal for hemoglobin. It could cause an increase or reduction in A1C values. Thalassemia could cause falsely lower A1C numbers due to the early degeneration of the red blood cells. Inform your doctor whether you know any relatives with Thalassemia.
Hemolysis (rapid destruction of red blood cells)
Hemolysis can falsely reduce A1C values because of the shorter life span of red blood cells. This could result from an ineffective immune response and synthetic heart valves.
Hypothyroidism that is not treated (low concentrations of thyroid hormone)
Hypothyroidism can falsely raise A1C levels, whereas treatments with thyroid hormone could reduce A1C. Talk to your physician about blood tests that evaluate thyroid function.
Pregnancy
The shorter lifespan of red blood cells and increased production could misleadingly lower A1C values in the late and early stages of pregnancy. Request the glucose test in your mouth, which can be used to diagnose gestational diabetes. One standard procedure for pregnant women who have diabetes is to utilize CGM.
Uremia (high levels of waste (usually eliminated by the kidneys) in the blood)
Untreated uremia can cause falsely high A1C values. Dialysis is a treatment for uremia. In this instance, A1C is not an appropriate test.
Medications
Medicines that could misleadingly increase A1C include:
- Opioids (pain relief agents) (pain relievers): Duragesic (fentanyl), Norco/Vicodin (hydrocodone), Dilaudid (hydromorphone), Astramorph/Avinza (morphine), OxyContin/Percocet (oxycodone)
- Long-term use of more than 500 mg aspirin a day or more
Medicines that can falsely lower A1C are:
- Erythropoietin (EPO)
- Azcone (dapsone)
- Virazole/Rebetol/Copegus (ribavirin)
- HIV medication (NRTIs): Emtriva, Epivir, Retrovir, Videx-EC, Viread, Zerit, or Ziagen
Always talk about the appropriate prescription of opioids to treat pain and their potential effect on A1C levels as well. Tell your doctor that you're taking any of these drugs before taking your A1C test.