Diabetes Management

Hemoglobin A1C: What is a Normal Level?

Your hemoglobin A1c levels are one of the most important things to know and to monitor as a diabetic.

Hemoglobin A1c is a blood test that your doctor runs every month or so to determine what is happening with your blood sugar levels.

Even small changes can have an effect and maintaining good control over blood glucose levels lowers the chances of experiencing diabetes complications.

This article will take a closer look at Hemoglobin A1c and outline 6 ways in which you can successfully lower your HbA1c levels.

What is the hemoglobin A1C test?

Type 1 and type 2 diabetes are associated with excursions in blood glucose levels.

That is, it is normal and healthy for circulating glucose levels in the body to be fairly tightly controlled (around 100 mg/dl or 5.6 mmol/L).

Yes, they will increase after meals, especially sugary ones, but they should fairly quickly normalize through the actions of insulin.

If the body doesn’t have enough insulin (type 1 or 2 diabetes) or insulin’s actions are not efficiently detected by the cell (type 2 diabetes), glucose can increase in the blood.

Chronically high or uncontrolled glucose in the bloodstream leads to modifications of blood proteins through a process known as glycosylation.

A major blood protein found in red blood cells is hemoglobin.

Glucose tends to bind to hemoglobin in a ratio proportionate to its circulating levels, resulting in glycosylated hemoglobin.

When this sugar becomes attached to Hb, it increases the molecular weight of the molecule and its ability to be detected by antibodies, allowing it to be detected by several chemical means.  

Once attached, glucose remains bound to the hemoglobin for the life of the red blood cell (about 120 days).  Thus, measuring its level can provide some information regarding how well a person has controlled their blood glucose levels over the course of the prior 3 months.

How does the hemoglobin A1C test work?

Over the last 40 years or so, doctors have begun to rely on the hemoglobin A1C test (in preference to fasting glucose or an oral glucose tolerance test) to diagnose diabetes and to obtain a better picture of how well a patient is controlling his blood glucose levels (over time).

A fasting blood glucose test registers only a brief “snapshot” in time, basically how well you fasted the night before the blood draw, and does not provide as integrative of a reflection of how well blood glucose has been controlled in the weeks and months preceding the exam, which provides a different perspective for both for the physician and the patient.

Blood is sampled at the office visit. One or more chemical assays measure the percent of hemoglobin that is bound to glucose.

How is the hemoglobin A1C test administered?

HbA1c tests are administered in your doctor’s office, although depending on the type of analysis being conducted, it may take a week or so for the results to come back.

No fasting is necessary before collection of blood for the Hemoglobin test, as the relative state of glycosylation cannot be reversed (for example by fasting overnight).

Why the A1C test is done

What is the hemoglobin A1C test used for?

Your doctor usually determines that a HbA1C test is warranted if she is concerned that your blood glucose is higher than suspected based on fasting glucose levels.

The HbA1c test is best used to predict a patient’s likelihood to develop microvascular complications associated with chronically high glucose levels.

Microvasculature includes the very smallest of blood vessels in the body, which if damaged, results in impairment in oxygen and nutrient delivery to cells. This can lead to cell and organ disease.

Organs susceptible to the damaging effects of high glucose include the kidney, the eye, the nervous system, the brain, and heart.  

Some of these diseases affect cells beyond the vasculature and include complications such as nephropathy, retinopathy, neuropathy, coronary disease.  

High glucose is damaging due to the development of oxidative stress and inflammation.  Inflammation, in itself, can result in scarring (fibrosis) and organ damage.

Furthermore, as mentioned earlier, glucose can bind to other proteins in addition to hemoglobin and result in damage to the function of those proteins, and thus the tissues and organ systems they reside in.  These physical moieties are known as advanced glycation end products (AGEs).

How often should you get an A1C test?

Under your doctor’s guidance, an A1C test is best conducted every 3-6 months, especially if you have had elevated A1C levels in the past or you currently have diabetes (type 1 or 2).

This allows times for the red blood cells to “turn over,” thus resetting the clock, and a providing you with the chance to reduce the levels, if needed.

Note that the glycation of hemoglobin itself is not necessarily known to cause problems with the function of the Hb (concerning its oxygen-carrying capacity), but it is like “the canary in the coal mine” and provides a sensitive, specific, biomarker for glucose levels in the blood over time.

Risk factors for type 2 diabetes include weight, age and family history. Therefore, it is reasonable for anyone especially over the age of 40 to be screened for A1C levels (especially if overweight) as sometimes fasting glucose tests can miss a propensity to have slow blood glucose clearance under the fed state, which presents a real risk for the microvasculature overtime.   

How can A1C testing help manage your diabetes?

The global prevalence of diabetes is over 400 million persons or around 8-9% of the population world-wide.

When you consider this is also generally a disease associated with aging, you can assume the incidence is much higher in persons over the age of 40.

So do not feel alone if you are struggling with how to maintain your health if you have diabetes.

At the opposite extreme, there are a number of persons in developing countries (in India alone around 70 million) that have type 2 diabetes but are not aware of the fact.

Once diabetes is suspected, an A1C test can help you manage your treatment and meal strategy to ensure that your glucose is tightly controlled around the clock.

Working closely with your physician and plotting your HbA1c over-time at different office visits, will allow you implement a diabetes treatment plan to titrate your medications, exercise, and diet to a level that maintains HbA1c in the normal range.  

What A1C test results mean

What is a normal A1C level?

HbA1c levels generally range from 4-14% (but may be higher) and can predict average blood glucose levels between 68 and 355 mg/dl.

For people without type 2 diabetes, the range is between 4 and 5.6%.  That is this proportion of their total Hb that is naturally bound to glucose given “normal circulating glucose levels.

A doctor may order a HbA1c test if he suspects that you may have pre-diabetes, i.e., your fasting (overnight) glucose is 100-125 mg/dl (5.6-7.0 mmol/L), you have other symptoms of microvascular disease, or you are overweight.  

Even this “pre-diabetic” glucose level can increase the glycosylation of Hb (and cause microvascular damage) over time.

You shouldn’t be concerned if you have a single slightly elevated A1C level, but rather a pattern of consistently elevated levels in the 6+ level indicates that your blood glucose is not as controlled as it should be.

An A1c level of 6 predicts average blood glucose of around 126 mg/dl, which would put you just above the pre-diabetic level.

Therefore, levels below 5 are fine and probably don’t need to be rechecked more frequently than your annual exam, but a level above that requires a discussion with your physician regarding retaking the measurement in 3 months.

Keeping blood sugar levels under control is very important for women who either have diabetes going into pregnancy or who develop diabetes during their pregnancy.

Therefore, if you are planning to become pregnant, as part of your diabetes management, you should be offered an HbA1c measurement on a monthly basis to help monitor your blood glucose control. If you are at risk for gestational diabetes, you may also have to take an oral glucose tolerance test (OGTT).

What do you do if your A1C levels are slightly elevated?

You do not need to panic if your A1C is consistently, but marginally above the ideal range.  There are several things you can do to reduce it. But remember the half-life of the red blood cell containing the glycosylated Hemoglobin A1C is 123 days, so don’t expect changes overnight.  

Wait to repeat the test for at least 3 months. If your A1C levels are between 5.7 and 6.4, you have a higher risk of developing diabetes in the future (if you are currently not diagnosed as diabetic).  

How much higher risk you have is uncertain and depends on a number of factors, including genetics, diet, age, and sex.

In addition to triggering a discussion with your doctor, a higher than normal hemoglobin A1C level can be reversed (at least somewhat) through exercise, weight loss, and adjustment in your medications if needed.  The most primary of these is to get your weight into an acceptable target range.

Reduce your BMI (body mass index) to less than 30.  Consultation with a dietician can help to formulate a menu and treatment plan that will have the best chance at success.

Exercise is important as well, to not only burn extra calories allowing you to eat a little more, but also increases muscle mass, insulin sensitivity, and metabolism, all effect that should reduce your average blood glucose levels.

What is a dangerous A1C level?

It is unclear that a high A1C is dangerous in itself, but may forebode bad things to come. The current target A1C level for persons with known diabetes is less than 7.  Poorly controlled diabetes is 8.0% or above.

There is a 10% decrease in the relative risk for microvascular complications for every 1% drop in A1C. Therefore, flipping the equation would predict a 10% increased risk for every 1% increase above 7.0%.  

Some people are more susceptible to microvascular complications given the same level of glycosylated Hb, which is why it is essential to keep in mind that it is only one test, one indication, and follow-up evaluations using additional measures should be conducted.

If you find your HbA1c enters the “poorly controlled” range, it would also be valuable to follow-up with specialists beyond your primary physician.

A nephrologist can help you gauge potential renal damage, and optometrists are trained to screen for retinopathy.  Wounds that are slow to heal are another side-effect or marker of “poorly-controlled” diabetes and can lead to amputation.   

Limits of the A1C test

What are the drawbacks of the A1C test?

Like any test, the HbA1c test has several limitations. First, the A1C test only provides an estimate of circulating glucose levels; it is not actually a measure of what those levels are.

It has been shown to correlate with glucose control, but it is a surrogate at best. Some persons/populations, e.g., African Americans and Asian, have been reported to have higher levels of glycosylated Hb relative to their circulating blood glucose levels.

Thus, the test may over-estimate the risk of microvascular complications in those people.

What can’t the A1C test tell you?

The A1C test also cannot explain short-term glucose excursions. For example, your glucose levels might fluctuate from the hyper to the hypo level multiple times during the day, but A1C can only provide feedback on the “average” glucose levels over time, which may be fine.

Wildly fluctuating blood glucose is dangerous for at least 2 reasons:

1) episodes of hypoglycemia can increase the risk for dizziness, falls, coma, and premature death.

2) undetected episodes of hyperglycemia (perhaps after meals) can still result in inflammation, oxidative stress, and protein modifications that damage the microvasculature.

Moreover, hyperglycemia can lead to dehydration if glucose is excreted in urine and takes a lot of water with it through the process of osmotic diuresis (increased urination).

What can you do to get a more complete picture of your health?

Therefore, there is clearly value in obtaining an A1C measurement, particularly if your fasting glucose frequently runs in the pre-diabetic range.

Nonetheless, this test is best employed in conjunction with traditional measures of fasting and non-fasting blood glucose readings, as well as, a glucose tolerance test to determine how rapidly a glucose load is cleared from your blood.  This is a significant indicator of insulin sensitivity.

A number of measures including blood pressure, heart rate, blood glucose, body weight, adipose distribution, and yes, perhaps blood A1C can contribute to a more complete picture of your general health.

Sources

  1. WebMD. (2019) High Blood Sugar, Diabetes, and Your Body.
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  4. Allen, J. (2010) A1c diabetes test is a better indicator of risk. Reuters
  5. Sandler, C. N., and McDonnell, M. E. (2016) The role of hemoglobin A1c in the assessment of diabetes and cardiovascular risk. Cleve Clin J Med 83, S4-S10
  6. Stehouwer, C. D. A. (2018) Microvascular Dysfunction and Hyperglycemia: A Vicious Cycle With Widespread Consequences. Diabetes 67, 1729-1741
  7. Prevention, C. f. D. C. a. (2018) All About Your A1C. In Diabetes
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  9. Finan, E., and Joseph, J. (2018) Glycosylated haemoglobin: a false sense of security. BMJ Case Rep 11
  10. Vigersky, R. A. (2019) Going beyond HbA1c to understand the benefits of advanced diabetes therapies. J Diabetes 11, 23-31

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