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Diagnostic Biomarker Profile

HbA1c Test (Glycated Hemoglobin)

A hemoglobin A1C (HbA1C) test is a blood test that shows your average level of blood glucose , also called blood sugar, over the past two to three months.

A hemoglobin A1C (HbA1C) test is a blood test that shows your average level of blood glucose , also called blood sugar, over the past two to three months. Glucose is a type of sugar in your blood that comes from the foods you eat. Your cells use glucose for energy. A hormone called insulin helps glucose get into your cells. If you have diabetes your body doesn't make enough insulin, or your cells don't use it well. As a result, glucose can't get into your cells, so your blood glucose levels increase. Glucose in your blood sticks to hemoglobin, a protein in your red blood cells. As your blood glucose levels increase, more of your hemoglobin will be coated with glucose. An A1C test measures the percentage of your red blood cells that have glucose-coated hemoglobin. An A1C test can show your average glucose level for the past three months because: Glucose sticks to hemoglobin for as long as the red blood cells are alive. Red blood cells live about three months. High A1C levels are a sign of high blood glucose from diabetes. Diabetes can cause serious health problems , including heart disease , kidney disease , and nerve damage . But with treatment and lifestyle changes, you can control your blood glucose levels. Other names: HbA1C, A1C, glycohemoglobin, glycated hemoglobin, glycosylated hemoglobin

Why is this test ordered? The Centers for Disease Control (CDC) recommends A1C testing for diabetes and prediabetes if: You are over age 45. If your results are normal, your provider will tell you how often you should be tested based on your age and risk factors. If your results show you have prediabetes, you will usually need to be tested every 1 to 2 years. Ask your provider how often to get tested and what you can do to reduce your risk of developing diabetes. If your results show you have diabetes, you should get an A1C test at least twice a year to monitor your condition and treatment. You are under 45 and are more likely to develop diabetes because you: Have prediabetes. Are overweight or have obesity . Have a parent or sibling with type 2 diabetes. Have high blood pressure or high cholesterol levels. Have heart disease or have had a stroke . Are physically active less than 3 times a week. Have had gestational diabetes (diabetes during pregnancy) or given birth to a baby over 9 pounds. Are African American, Hispanic or Latino, American Indian, or an Alaska Native person. Some Pacific Islander and Asian American people also have a higher risk of developing diabetes. Have polycystic ovarian syndrome (PCOS). You may also need an A1C test if you have symptoms of diabetes, such as: Feeling very thirsty Urinating (peeing) a lot Losing weight without trying Feeling very hungry Blurred vision Numb or tingling hands or feet Fatigue Dry skin Sores that heal slowly Having more infections than usual

Reference Ranges & Biomarker Tiers

Adult reference interval: Below 5.7%

NormalBelow 5.7%Below the diagnostic threshold for prediabetes.
Prediabetes5.7% to 6.4%NIDDK diagnostic band for prediabetes.
Diabetes6.5% or aboveMeets the NIDDK diagnostic threshold for diabetes. Diagnosis requires a confirming second measurement unless clear symptoms are present.

Reference intervals vary by performing laboratory, assay method, age and sex. Always interpret a result against the interval printed on the report from the laboratory that ran the test. Source for these values: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), NIH.

Clinical Interpretation

A1C results tell you what percentage of your hemoglobin is coated with glucose. The ranges are just a guide to what is normal. What's normal for you depends on your health, age, and other factors. Ask your provider what A1C percentage is healthy for you. To diagnose diabetes or prediabetes, the percentages commonly used are: Normal: A1C below 5.7% Prediabetes: A1C between 5.7% and 6.4% Diabetes: A1C of 6.5% or higher Providers often use more than one test to diagnose diabetes. So, if your test result was higher than normal, you may have another A1C test or a different type of diabetes test , usually either a fasting blood glucose test or an oral glucose tolerance test (OGTT). If your A1C test was done to monitor your diabetes, talk with your provider about what your test results mean. Learn more about laboratory tests, reference ranges, and understanding results .

Medicare NCD code list — diagnoses CMS lists as supporting medical necessity

D13.7Benign neoplasm of endocrine pancreasMedicare medical-necessity (NCD 190.21)E08.00Diabetes mellitus due to underlying condition with hyperosmolarity without nonketotic hyperglycemic-hyperosmolar coma (NKHHC)Medicare medical-necessity (NCD 190.21)E08.01Diabetes mellitus due to underlying condition with hyperosmolarity with comaMedicare medical-necessity (NCD 190.21)E08.10Diabetes mellitus due to underlying condition with ketoacidosis without comaMedicare medical-necessity (NCD 190.21)E08.11Diabetes mellitus due to underlying condition with ketoacidosis with comaMedicare medical-necessity (NCD 190.21)E08.21Diabetes mellitus due to underlying condition with diabetic nephropathyMedicare medical-necessity (NCD 190.21)E08.22Diabetes mellitus due to underlying condition with diabetic chronic kidney diseaseMedicare medical-necessity (NCD 190.21)E08.29Diabetes mellitus due to underlying condition with other diabetic kidney complicationMedicare medical-necessity (NCD 190.21)E08.311Diabetes mellitus due to underlying condition with unspecified diabetic retinopathy with macular edemaMedicare medical-necessity (NCD 190.21)E08.319Diabetes mellitus due to underlying condition with unspecified diabetic retinopathy without macular edemaMedicare medical-necessity (NCD 190.21)E08.3211Diabetes mellitus due to underlying condition with mild nonproliferative diabetic retinopathy with macular edema, right eyeMedicare medical-necessity (NCD 190.21)E08.3212Diabetes mellitus due to underlying condition with mild nonproliferative diabetic retinopathy with macular edema, left eyeMedicare medical-necessity (NCD 190.21)E08.3213Diabetes mellitus due to underlying condition with mild nonproliferative diabetic retinopathy with macular edema, bilateralMedicare medical-necessity (NCD 190.21)E08.3291Diabetes mellitus due to underlying condition with mild nonproliferative diabetic retinopathy without macular edema, right eyeMedicare medical-necessity (NCD 190.21)E08.3292Diabetes mellitus due to underlying condition with mild nonproliferative diabetic retinopathy without macular edema, left eyeMedicare medical-necessity (NCD 190.21)E08.3293Diabetes mellitus due to underlying condition with mild nonproliferative diabetic retinopathy without macular edema, bilateralMedicare medical-necessity (NCD 190.21)E08.3311Diabetes mellitus due to underlying condition with moderate nonproliferative diabetic retinopathy with macular edema, right eyeMedicare medical-necessity (NCD 190.21)E08.3312Diabetes mellitus due to underlying condition with moderate nonproliferative diabetic retinopathy with macular edema, left eyeMedicare medical-necessity (NCD 190.21)

Showing 18 of 603 diagnoses CMS lists as covered for this test under NCD 190.21. The complete list is in CMS's Lab NCD code list; a listing is CMS's published code list, not a coverage determination for any claim.

Clinical Protocol & Patient Advice

  • 1

    Fasting is not required for the HbA1c test. You may eat and drink normally prior to blood draw.

  • 2

    This test can be performed at any time of day, regardless of food intake.

  • 3

    Certain medicines such as opioids and some HIV medicines may affect your results, so tell your provider about everything you take. But don't stop taking any medicines unless your provider tells you to. Also, let your health care provider know if you are pregnant, since this may affect your results.

Usage Guidance

  • This test is commonly associated with glycemic homeostasis and diabetes mellitus evaluation.
  • Elevated levels may be seen in chronic insulin resistance, metabolic syndrome, or prediabetes.
  • Always discuss your specific laboratory results and individual target ranges with a qualified healthcare professional.
  • Reference ranges vary by laboratory. Always discuss your specific results with a qualified healthcare professional.

Source: MedlinePlus, National Library of Medicine. View the original.

Read from: MedlinePlus (NLM); reference ranges only where NIDDK, NIH ODS or NCI states the value, linked per page — Curated from federal sources. All data sources · How to read the labels

Current data releases:ICD-10-CM FY2027 · ICD-10-PCS FY2027 · HCPCS October 2026 · MS-DRG v44 · Medicare Code Editor v44.0 · NCCI PTP Q4 2026 · MUE Q4 2026 · NCD code lists 2026-01 · LCD export September 28, 2026 · All releases and sources