Hemoglobin A1c (HbA1c) calculated from whole blood using a mass fraction measurement
This test measures the average blood sugar (glucose) levels over the past 2–3 months by analyzing a protein in your red blood cells called hemoglobin. It helps doctors assess long-term blood sugar control, especially useful for managing diabetes.
["This test gives a snapshot of how well your blood sugar has been controlled over time."]
Key facts at a glance
- LOINC
- 41655-2
- Short code
- Hct VFr BldMV Calc
- Synonyms
- Hct VFr BldMV Calc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 36
- Ref high
- 50
- Critical range
- 18 N/A – 60 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- calculated
- CPT
- 85014
- 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?
Doctors order HbA1c tests primarily to diagnose diabetes, monitor treatment progress, or check for undiagnosed high blood sugar. It’s a key tool for long-term diabetes management because it reflects average glucose levels over time, unlike daily blood sugar checks.
How Is This Test Performed?
A small blood sample is taken from your arm, typically during a routine visit to your healthcare provider’s office. The blood is processed to measure the percentage of hemoglobin that is coated with glucose, which is then used to calculate your HbA1c level.
What Does an HbA1c Result Mean?
Results are usually reported as a percentage. While specific ranges vary by lab and individual health, higher percentages generally indicate poorer blood sugar control. For example, levels above 6.5% may suggest diabetes, while levels below 5.7% are often considered normal.
What Are Common Causes of Abnormal Results?
Several factors can affect HbA1c results, including recent blood sugar fluctuations, anemia, hemoglobin disorders, pregnancy, or certain medications. If your result seems unusually high or low, discuss it with your doctor to rule out these influences.
Reference range
Adult males: 38-50%; Females: 36-44%N/A
No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
HbA1c (Calculated)
Frequently asked questions
How often should I get an HbA1c test?
Can HbA1c test results change if I’ve recently had a blood donation?
What if my HbA1c result is outside the normal range?
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 17, 2026. · Read our editorial policy