Hemoglobin A1c (HbA1c) Glycosylated Hemoglobin Assay
This test measures the percentage of hemoglobin in your blood that has been attached to sugar (glucose), reflecting your average blood sugar levels over the past 2–3 months.
["HbA1c helps doctors track diabetes management and long-term blood sugar control."]
Key facts at a glance
- LOINC
- 62854-5
- Short code
- Glycosylated hemoglobin assay
- Synonyms
- Glycosylated hemoglobin assay
- Category
- glucose
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 12
- Ref high
- 17.5
- Critical range
- 7 N/A – 20 N/A
- Fasting
- true
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- phenx
- CPT
- 85018
- SNOMED
- 900000000000003004
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Your doctor may order an HbA1c test to diagnose diabetes, monitor diabetes treatment, or check for prediabetes. It’s especially useful because it provides a snapshot of your blood sugar control over time, unlike a single blood sugar reading.
How Is the Test Performed?
A small blood sample is taken from your arm, usually during a routine blood draw. The test measures the proportion of hemoglobin molecules linked to glucose, which is stable in blood and doesn’t change with movement or time.
What Do the Results Mean?
Results are reported as a percentage, indicating your average blood sugar levels over the past few months. While specific ranges vary by lab and health status, higher percentages suggest higher blood sugar control issues.
Common Causes of Abnormal Results
Elevated HbA1c may indicate diabetes, poor diabetes management, or conditions like kidney disease or anemia. Lower-than-expected levels might suggest underdiagnosed diabetes or certain blood disorders.
Reference range
Adult males: 13.5-17.5 g/dL; Females: 12.0-16.0 g/dLN/A
No special preparation required. Stay well hydrated.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: HbA1c is a critical tool for diabetes care because it reflects long-term glucose exposure, helping doctors adjust treatments like insulin or diet to improve health outcomes and reduce complications like nerve damage or heart disease.
Short name
HbA1c
Frequently asked questions
How often should I get an HbA1c test if I have diabetes?
What factors could affect my HbA1c results?
Can I prepare for this test in any way?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy