How Blood Glucose Levels Relate to Diabetes and the Importance of the A1c Blood Test

Research has shown that maintaining blood glucose levels within an acceptable range can lower and delay your risk for complications. You and your physician must decide what blood glucose levels are achievable for you based on your age, abilities, medical status, personal needs, and any other special circumstances.

The currently acceptable blood glucose target ranges set by the American Diabetes Association (ADA) are as follows:

  • Fasting/pre-meal: between 80 and 130 mg/dL
  • One to two hours after a meal: below 180 mg/dL

It is important to remember that the purpose of your blood glucose readings is to let you know how close you are to your target range. Try not to label your readings as either “bad” or “good”; instead, think of them as indicators that describe (a) which aspects of your treatment are working for you and (b) which aspects need to be changed.

A1c Blood Test

by Audrey Demmitt, R.N. updated 11/22

The A1c blood test, also known as glycated hemoglobin, hemoglobin A1c, and HbA1c, is the primary tool used to diagnose diabetes and pre-diabetes and to monitor blood glucose control in people with type 1 and type 2 diabetes. This test enables healthcare providers to diagnose diabetes and treat it before complications occur and to diagnose pre-diabetes to prevent or delay the development of type 2 diabetes. Below are the established A1c levels used to diagnose diabetes and pre-diabetes:

DiagnosisA1c level
Normalbelow 5.7 percent
Pre-diabetes5.7 to 6.4 percent
Diabetes6.5 percent or above

Table showing diagnosis and A1lc level: normal: below 5.7%; pre-diabetes 5.7-6.4%; diabetes 6.5% or above
Source: American Diabetes Association

How Does the A1c Compare to Other Blood Glucose Tests?

Several other traditional blood glucose tests are used to diagnose and manage diabetes: the fasting and random blood glucose tests, the glucose tolerance test, and the self-monitoring home glucose test. These can be thought of as snapshots, measuring the blood sugar level in a moment or day to day.

Normal blood glucose levels range from 80-100mg/dL (milligrams per deciliter), fluctuating throughout the day in response to food, activity, medication, illness, and stress. Daily readings are interpreted in the short term to monitor blood sugar changes. It is helpful to do daily testing and record the values to reveal patterns and responses so that you can take corrective actions and adjust your daily care plan.

In contrast, A1c is a long-term average of blood glucose levels and gives a “big picture” perspective on how well you control daily blood sugars. It can be useful in evaluating the overall success of the treatment plan, your daily efforts, and the efficacy of medications.

How Does the A1c Relate to My Daily Blood Sugars?

Your A1c can be converted to a number expressed in the same terms as your daily blood glucose readings. This is called “estimated average glucose” or eAG. For example, an A1c of 7% is equivalent to an estimated average glucose (eAG) of 154 mg/dL, reflecting blood sugars that may have ranged between 180 and 140 mg/dL over the past three months.

The A1c/eAG is not the same as the average blood glucose you may see on your meter since it averages all the blood sugar levels – not just the ones you may have recorded on your meter. The average blood glucose reported on your meter is likely to be lower than your actual A1c/eAG.

Maintaining blood sugars as close to the normal range as possible is the goal of reducing the risks and complications of diabetes. When daily blood sugars are kept in the optimal range, the corresponding A1c will also be optimal. Below is a table with conversions of A1c levels to eAG.

A1c in percenteAG in mg/dL

(Source: Adapted from American Diabetes Association. Standards of medical care in diabetes—2014. Diabetes Care. 2014;37(Supp 1):S14–S80, table 8.)

How Often Should My A1c Be Tested?

The American Diabetes Association (ADA) recommends you have the A1c test twice yearly if your blood sugars are stable and you are meeting your treatment goals. Healthcare providers may repeat the A1c test as often as four times a year if there are changes in treatments or you are not meeting your A1c target. The A1c is like a report card on how well you are managing your diabetes.

What Should My Target A1c Be?

Everyone will not have the same A1c target. It will depend on your individual diabetes history and general health. You and your doctor need to discuss this and set appropriate goals for your situation.

The ADA suggests a target A1c below 7%. Research shows that keeping A1c levels below 7% can reduce complications of diabetes. But an A1c of 7% or below may not be safe or realistic for everyone. Less strict control may be suitable for older persons, those who experience severe hypoglycemic (low blood sugar) episodes, or those with advanced diabetes complications, for example.

People who are younger and have had diabetes for a shorter time may have a target A1c of 6.5% or below, according to the ADA recommendations. The key is to make sustained daily efforts to achieve the best target for you.

By making daily efforts to stick to your treatment plan and healthy lifestyle changes, you can achieve your A1c goal, avoid long-term complications, and live well with diabetes. Here are some additional resources:

By Debra A. Sokol-McKay,
MS, CDE, OTR/L, SCLV, updated December 2022 by Kim Ladd, RN, BS, CPHQ, CDCES