HbA1c blood test

A blood test that shows your average blood sugar level over the past two to three months. It is used to screen for and diagnose type 2 diabetes and prediabetes, and to monitor people who have diabetes.

Also called HbA1c · A1C · Glycated hemoglobin · Hemoglobin A1C

Biomarker
In this atlas

Overview

Technical summary

Glycated hemoglobin: the percentage of red blood cells whose hemoglobin carries glucose. In the trials on this site it describes who was enrolled and how treatment changed blood sugar: the SURPASS-CVOT abstract reports a mean baseline level of 8.4 percent, and Look AHEAD reported greater reductions in glycated hemoglobin with its lifestyle intervention.

What is measured

Measure: The percentage of red blood cells that have glucose-coated hemoglobin.
Assay context: A blood test. It shows the average blood glucose level over about three months because red blood cells live about three months.

Interpretation

Description Evidence stage not applicable Certainty not assessed

MedlinePlus says an HbA1c test is a blood test that shows the average level of blood glucose over the past two to three months. It may be used to screen for or diagnose type 2 diabetes and prediabetes, and to help monitor people who have diabetes or prediabetes. It is not used to diagnose type 1 diabetes but may be used to monitor blood glucose levels in type 1 diabetes.
Applies to Mixed recipients
- People who are screened for diabetes or prediabetes with an HbA1c test, and people with diabetes or prediabetes whose condition is monitored with it.
- Not stated; patient information page
- Not stated; United States federal health agency
- All ages; the page gives screening advice by adult age and risk factors
- Gestational age Not reported
- Postnatal age Not reported
Follow-up Not applicable (descriptive page)
Certainty method
Not assessed

Limitations
A patient-information page from the National Library of Medicine. It gives no diagnostic cut-off values in the passages read, so this atlas gives none.

Last checked
2026-10-14

Next evidence check due
Not scheduled
Sources and citations (2)
1. Supports MedlinePlus medical test: Hemoglobin A1C (HbA1c) Test
  
  Webpage · U.S. National Library of Medicine (MedlinePlus) · Edition MedlinePlus page fetched 2026-10-14; the page footer says last updated May 20, 2025.
  
  Locator
  What is a hemoglobin A1C (HbA1C) test?, para 1
  
  How it applies
  What the test shows.
  
  Retrieved
  2026-10-14T18:30:06Z
  
  Source effective date
  Not reported
  
  Source state
  Current
  
  Snapshot hash
  8b1bc8bb2e92a787e188524a111fd92d7ba8a494de0ff76c36e312f4cd52948a
  
  Reuse basis
  The MedlinePlus page on using its content (fetched 2026-10-14 as ch-medlineplus-usingcontent.html, sha256 31267ce9db01, hash only) says works produced by the federal government are not copyrighted, and lists summaries on health topic pages and medical test information as public domain; A.D.A.M. Medical Encyclopedia articles are copyrighted, and this atlas cites none. Please acknowledge MedlinePlus, National Library of Medicine, as the source. The raw page is committed at research/snapshots/ch-medlineplus-hba1c-test.html.
2. Supports MedlinePlus medical test: Hemoglobin A1C (HbA1c) Test
  
  Webpage · U.S. National Library of Medicine (MedlinePlus) · Edition MedlinePlus page fetched 2026-10-14; the page footer says last updated May 20, 2025.
  
  Locator
  What is it used for?, para 2; What is it used for?, para 3; What is it used for?, para 4; What is it used for?, para 5
  
  How it applies
  Uses of the test, and the exception for diagnosing type 1 diabetes.
  
  Retrieved
  2026-10-14T18:30:06Z
  
  Source effective date
  Not reported
  
  Source state
  Current
  
  Snapshot hash
  8b1bc8bb2e92a787e188524a111fd92d7ba8a494de0ff76c36e312f4cd52948a
  
  Reuse basis
  The MedlinePlus page on using its content (fetched 2026-10-14 as ch-medlineplus-usingcontent.html, sha256 31267ce9db01, hash only) says works produced by the federal government are not copyrighted, and lists summaries on health topic pages and medical test information as public domain; A.D.A.M. Medical Encyclopedia articles are copyrighted, and this atlas cites none. Please acknowledge MedlinePlus, National Library of Medicine, as the source. The raw page is committed at research/snapshots/ch-medlineplus-hba1c-test.html.

Clinical links

Each link reports what one cited claim says about one population. "Evaluated for" means studied, not shown to work. These links do not show that anything is effective or right for you.

Claim, not a settled fact Used to screen for, diagnose and monitor type 2 diabetes: Type 2 diabetes (Evaluated for)
Applies to Mixed recipients
- People who are screened for diabetes or prediabetes with an HbA1c test, and people with diabetes or prediabetes whose condition is monitored with it.
- Not stated; patient information page
- Not stated; United States federal health agency
- All ages; the page gives screening advice by adult age and risk factors
- Gestational age Not reported
- Postnatal age Not reported
Follow-up Not applicable (descriptive page)
MedlinePlus says an HbA1c test is a blood test that shows the average level of blood glucose over the past two to three months. It may be used to screen for or diagnose type 2 diabetes and prediabetes, and to help monitor people who have diabetes or prediabetes. It is not used to diagnose type 1 diabetes but may be used to monitor blood glucose levels in type 1 diabetes.
Limitations. A patient-information page from the National Library of Medicine. It gives no diagnostic cut-off values in the passages read, so this atlas gives none.

Record details

Record id: cardio:hba1c
Content hash: 97d1f0ef0599b2c4bed63a7ae69301a04163159c4a86d31b8d8b217dbf36489f