# HbA1c blood test

Biomarker · id `cardio:hba1c` · Cardiovascular Atlas · release `f6f6f1b6f50379ed` (public)

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Also called: HbA1c; A1C; Glycated hemoglobin; Hemoglobin A1C

Browse, organ or system: Metabolism  
Browse, condition area: Diabetes and metabolic disease  

## In plain language

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.

## 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 a trial of a lifestyle intervention reported greater reductions in glycated hemoglobin.

## Claims, with the population each applies to

## Context: People being screened for, or living with, diabetes or prediabetes (MedlinePlus test page)

Recipient: Mixed recipients; Population: People who are screened for diabetes or prediabetes with an HbA1c test, and people with diabetes or prediabetes whose condition is monitored with it.; Care setting: Not stated; patient information page; Geography: Not stated; United States federal health agency; Life stage: 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.

- Category: Description
- Evidence stage: Evidence stage not applicable
- Certainty: Certainty not assessed
- Applies to: Recipient: Mixed recipients; Population: People who are screened for diabetes or prediabetes with an HbA1c test, and people with diabetes or prediabetes whose condition is monitored with it.; Care setting: Not stated; patient information page; Geography: Not stated; United States federal health agency; Life stage: 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)
- 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
- Sources:
  1. Supports: MedlinePlus medical test: Hemoglobin A1C (HbA1c) Test (Webpage, edition MedlinePlus page fetched 2026-10-14; the page footer says last updated May 20, 2025.) <https://medlineplus.gov/lab-tests/hemoglobin-a1c-hba1c-test/>
     Locator: What is a hemoglobin A1C (HbA1C) test?, para 1. Retrieved 2026-10-14T18:30:06Z. Source state: Current. Snapshot hash: 8b1bc8bb2e92a787e188524a111fd92d7ba8a494de0ff76c36e312f4cd52948a.
     How it applies: What the test shows.
  2. Supports: MedlinePlus medical test: Hemoglobin A1C (HbA1c) Test (Webpage, edition MedlinePlus page fetched 2026-10-14; the page footer says last updated May 20, 2025.) <https://medlineplus.gov/lab-tests/hemoglobin-a1c-hba1c-test/>
     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. Retrieved 2026-10-14T18:30:06Z. Source state: Current. Snapshot hash: 8b1bc8bb2e92a787e188524a111fd92d7ba8a494de0ff76c36e312f4cd52948a.
     How it applies: Uses of the test, and the exception for diagnosing type 1 diabetes.

## Connected pages

- Used to screen for, diagnose and monitor type 2 diabetes: Type 2 diabetes (`cardio:type-2-diabetes`) [a claim, not a settled fact; see claim `cardio:claim-hba1c-use` and its context]
- Related to: MedlinePlus (`core:medlineplus`)
- Investigated in: SURPASS-CVOT: tirzepatide against dulaglutide on major cardiovascular events (`cardio:surpass-cvot`)

## Provenance

Content hash: c70ebf205bdac60008f714ffa8e0254e6f69c8f19f8fbe4c06e3780422dd6bb1
Last substantive edit: 2026-10-15
Evidence last checked: Not recorded