hemoglobin A1c

noun

: a stable glycoprotein formed when glucose binds to hemoglobin A in the blood

Blood sugar was assessed by measuring the amount of hemoglobin A1c in the participants' blood, a test that looks for hemoglobin with sugar attached to it.

—Gina Kolata

also : a test that measures the level of hemoglobin A1c in the blood as a means of determining the average blood sugar concentrations for the preceding two to three months

Note: Both the glycoprotein and the test are also called A1c, glycated hemoglobin, glycohemoglobin, glycosylated hemoglobin, HA1c, and HbA1c.

Examples of hemoglobin A1c in a Sentence

Recent Examples on the Web

Cinnamon and cinnamon extracts have been reported in multiple trials and reviews to modestly lower fasting glucose and hemoglobin A1c (average blood sugar level over two or three months) in some people. —Sara Hoffman, Verywell Health, 31 Dec. 2025

Several research studies have shown that the ketogenic diet can help reduce hemoglobin A1c (HbA1c, a measure of your blood sugar over several months) and body weight compared to standard diets.345 Like keto, intermittent fasting may also help improve your blood sugar and weight to some degree. —Heidi Cope, Health, 25 Dec. 2025

Orforglipron met the trial’s other goals of reducing patients’ hemoglobin A1c, a measure of blood sugar levels. —Joshua P. Cohen, Forbes.com, 2 Sep. 2025

Word History

First Known Use

1964, in the meaning defined above

Medical Definition

hemoglobin A1c

noun

-ˌā-ˌwən-ˈsē

: a stable glycoprotein formed when glucose binds to hemoglobin A in the blood

Blood sugar was assessed by measuring the amount of hemoglobin A1c in the participants' blood, a test that looks for hemoglobin with sugar attached to it.

—Gina Kolata

also : a test that measures the level of hemoglobin A1c in the blood as a means of determining the average blood sugar concentrations for the preceding two to three months

called also A1c, glycated hemoglobin, glycohemoglobin, glycosylated hemoglobin, HA1c, HbA1c