The A1C test measures the percentage of your red blood cells that carry glucose-coated (sugar-coated) hemoglobin — hemoglobin being the oxygen-carrying protein inside red blood cells — which reflects your average blood sugar over the past 3 months (Centers for Disease Control and Prevention, 2024-05-15). It is reported as a percentage (%), and the cutoffs that separate normal, prediabetes and diabetes appear on your lab report alongside your own number.
This guide explains the categories in general terms and what typically happens after each one. What your particular result means belongs to your doctor, who has your full history and other results.
What This Test Measures
A1C is reported as a percentage (%) — the share of your hemoglobin that is glucose-coated. The specific cutoff numbers for each band are set by bodies such as the Centers for Disease Control and Prevention and the American Diabetes Association, and your lab prints the ones it uses next to your result.
Result Range
What It May Indicate
Typical Next Step
Normal band, in % (below your lab's prediabetes cutoff)
Average blood sugar over about three months in the range used as normal for diagnosis purposes (Centers for Disease Control and Prevention, 2024-05-15; a normal level is also stated by the National Institute of Diabetes and Digestive and Kidney Diseases)
Your doctor decides repeat timing based on your risk factors and other results
Prediabetes band, in % — the borderline range between normal and diabetes (Centers for Disease Control and Prevention, 2024-05-15; American Diabetes Association, 2026)
Blood sugar higher than the normal band but not in the diabetes band
The doctor will likely recommend repeating the A1C test on a set interval (Centers for Disease Control and Prevention, 2024-05-15)
Diabetes band, in % (Centers for Disease Control and Prevention, 2024-05-15)
A result in the range used to diagnose diabetes
Two abnormal results at two different times are required for a diagnosis (MedlinePlus, National Library of Medicine); a clinician may use two A1C tests, or an A1C plus another test such as a fasting blood sugar test (Mayo Clinic)
Above the A1C treatment goal your doctor has set, in %, if you already have diabetes (Centers for Disease Control and Prevention, 2024-05-15)
Often means blood sugar is not as well controlled as would be ideal (MedlinePlus, National Library of Medicine)
Review of your care plan; most people with diabetes have A1C tested at a set minimum frequency (Centers for Disease Control and Prevention, 2024-05-15)
Notes on these ranges:
The bands are a guide, and what is normal depends on a person's health, age and other factors (MedlinePlus, National Library of Medicine). Cutoffs and reporting can also differ between labs and methods.
For diagnosis, the test should use a method that is NGSP certified and standardized to the DCCT assay — a national standardization programme for A1C testing (American Diabetes Association, 2026). Samples analysed in a doctor's office or clinic, known as point-of-care tests, should not be used to diagnose diabetes (National Institute of Diabetes and Digestive and Kidney Diseases).
A1C should not be used to diagnose type 1 diabetes, gestational diabetes (diabetes first appearing in pregnancy), or cystic fibrosis-related diabetes (National Institute of Diabetes and Digestive and Kidney Diseases).
The A1C draw does not require fasting, though other tests done at the same visit might (Centers for Disease Control and Prevention, 2024-05-15).
What Can Affect Your Result
Several things other than blood sugar can push an A1C result up or down, or make it less exact:
Anemia, including severe anemia — a low red blood cell count (Centers for Disease Control and Prevention, 2024-05-15; Mayo Clinic).
Inherited hemoglobin conditions such as sickle cell anemia or thalassemia, and other forms of hemoglobin in the body (Centers for Disease Control and Prevention, 2024-05-15; Mayo Clinic).
Recent or heavy blood loss, or a recent blood transfusion (Centers for Disease Control and Prevention, 2024-05-15; Mayo Clinic).
Pregnancy, particularly early or late pregnancy (Centers for Disease Control and Prevention, 2024-05-15).
Kidney failure or liver disease (Centers for Disease Control and Prevention, 2024-05-15).
Certain medicines, including opioids and some HIV medicines (Centers for Disease Control and Prevention, 2024-05-15).
The testing method itself — a point-of-care fingerstick is not used for diagnosis (National Institute of Diabetes and Digestive and Kidney Diseases). Where the link between A1C and actual blood sugar is altered — some hemoglobin variants, pregnancy, glucose-6-phosphate dehydrogenase (G6PD) deficiency, HIV, and conditions that change how fast red blood cells turn over — plasma glucose criteria should be used to diagnose diabetes instead of A1C (American Diabetes Association, 2026).
Questions to Ask Your Doctor About This Result
Take the printed report with you and work through these in order:
"What does my A1C mean when you read it alongside my other results and my medical history?"
"Do any of my conditions, medicines or recent blood loss make this A1C less reliable for me?"
"Was this run on a lab method that can be used for diagnosis, or was it a point-of-care fingerstick?"
"What is the next test or monitoring step, and when exactly should I come back for it?"
"If I already have diabetes, what A1C goal are you setting for me, and what is that based on?"
"Which symptoms should make me call your office the same day, and which should send me to an emergency department?"
Ask question 6 before you leave. As a general marker, vomiting you cannot keep down, deep or rapid breathing, fruity-smelling breath, confusion or unusual drowsiness, or sudden shakiness and sweating with confusion are reasons to seek same-day medical contact or emergency care rather than wait for a scheduled follow-up.
Frequently asked questions
Do I need to fast before an A1C test?
The A1C test does not require fasting beforehand, although other tests ordered at the same visit might (Centers for Disease Control and Prevention, 2024-05-15). Check the instructions your clinic gives you, and confirm with your doctor, who has your full history and other results.
Does one high A1C mean I have diabetes?
Two abnormal A1C results at two different times are required for a diagnosis (MedlinePlus, National Library of Medicine), and a clinician may instead pair an A1C with another test such as a fasting blood sugar test (Mayo Clinic). Whether a repeat or a different test applies to you is a decision for your doctor, who has your full history and other results.
Why is my number interpreted differently from someone else's?
The bands are a guide, and what is normal depends on a person's health, age and other factors (MedlinePlus, National Library of Medicine); labs also differ in the method and reference range they report. Comparing your percentage with a friend's leaves out that context, so bring the question to your doctor, who has your full history and other results.
How often is A1C repeated?
If a result falls in the prediabetes range, the doctor will likely recommend repeating the A1C on a set interval, and most people with diabetes have their A1C tested at a set minimum frequency (Centers for Disease Control and Prevention, 2024-05-15). Your own schedule is set by your doctor, who has your full history and other results.
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