Hemoglobin A1C (HgbA1c): The Ultimate Guide

Also Known As: A1c and HgbA1c

The A1C test is nothing more than a simple blood test. It’s used to diagnose diabetes.

It monitors the progress of a treatment plan.

It also reflects the average blood sugar levels in the past 3-4 months.

A1C is a type of glycated hemoglobin. In laymen’s terms, this is just hemoglobin bound to glucose.

Hemoglobin is nothing other than a protein of red blood cells. A1C forms as a result of how red blood cells and sugar in the blood.

The higher your blood glucose, the more glucose binds to hemoglobin. This results in an increase in the amount of A1C.

The test reports the percentage of hemoglobin that is bound to glucose. Once hemoglobin is glycated, it remains that way in the blood until the red blood cell carrying it is removed from the circulation.

The typical lifespan of a red blood cell is 3 to 4 months.

This means the A1C can be used to determine blood glucose status for the past 3-4 months.

When blood glucose rises, some of the glucose attaches permanently to the hemoglobin in red blood cells, which lasts for the lifetime of the red blood cell.

An average blood glucose level corresponds to an A1C result of less than 5.7%.

An A1C level greater than 6.5% indicates diabetes. Between 5.7 and 6.5% is prediabetes. An estimated average glucose level, eAG, measured in concentration units:

  • Milligrams per deciliter
  • Millimoles per liter

It can be calculated and often reported in addition to the A1C percentage. Estimated Average Glucose (eAG) is interesting because it helps doctors link A1C to the average blood sugar over the past 3 to 4 months.

Here’s the formula:

  28.7 x HbA1c — 46.7 = eAG (in mg/dl)

For Example:

I had a patient in the ICU one time with an A1C of 16.

That means they were walking around with a blood sugar of over 400 for the past 3 months. Yikes

The point is:

A1C is an essential lab value used to help managing diabetes. For a diabetic patient, the goal is to get A1C down below 7%.

However, when setting goals with your doctor, your age and other health conditions must be considered.

Typically, younger patients who don’t have low glucose issues (hypoglycemia) need less stringent goals to avoid diabetes complications in the future.

If you have frequent low-glucose episodes or an increased age, you will typically have a higher goal.

So keep in mind:

Several factors affect the accuracy of your A1C test result.

People with blood disorders, such as:

  • Sickle cell disease
  • Thalassemia or
  • Hemolytic anemia

… may have a lower than expected A1C.

This is due to the shorter lifespan of red blood cells. On the other hand, iron deficiency anemia is associated with increased red blood cell lifespan and falsely high A1C measurements.

Speaking of lifespan:

If you had access to a single data point and needed to predict someone’s odds of dying…

What would you choose?

The mainstream view would probably be cholesterol. I’d choose insulin resistance.

A team of researchers had a similar idea.

In their study, dubbed EPIC-Norfolk, they followed over 4500 men aged 45 to 79. They measured their HbA1c.

So what happens when you measure A1c in a group of men and then see who died?

You find some staggering results.

Each 1% increase in HbA1c is associated with a 28% increased risk of death in any given period.

Keep in mind that this is death from any cause.

Two points here (besides the apparent increase in death):

Number 1: When you hear A1c, you usually think of prediabetes and diabetes, right? Turns out, death rates rose even below the level of prediabetes or diabetes.

This means you could be at higher risk of poor outcomes…

Even if your doctor doesn’t think your blood glucose or HbA1c is too high.

Number 2: The increase in death rates was continuous. Any increase in HbA1c means a higher death rate.

This points to causation, not just association.

So if you want to be around for a long time and avoid chronic illness, then taking control of your blood sugar should be your #1 health priority.

Some people may have distinctive forms of hemoglobin that produce falsely high or low results. They include:

  • African Americans
  • Mediterranean ethnicities or
  • Southeast Asians

Certain liver and kidney problems may affect the turnover rate of red blood cells. This will often result in incorrect A1C readings.

Bleeding disorders or a recent blood transfusion will also skew the test results.

Note: A blood sample is taken. No preps are required before this test.

David Becker, RN, CCRN
David Becker, RN, CCRN Mr. Becker is a father, husband, and CCRN in Trauma ICU. You can read his inspiring comeback story From 412ng/dl To 923ng/dl In 6 Months - Without TRT. Feel free to send David a message here.