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Hemoglobin A1c (HbA1c) from whole blood by high-performance liquid chromatography (HPLC)

Published: August 9, 2026Updated: August 16, 2026

This test measures the average blood sugar level over the past 2 to 3 months by examining your red blood cells.

Quick summary

["HbA1c reflects your long-term blood sugar control and helps doctors track diabetes management."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
34734-4
Short code
Deprecated APOE Gentyp Bld/T-Imp
Synonyms
Deprecated APOE Gentyp Bld/T-Imp
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
molgen
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Doctors order HbA1c tests primarily to diagnose type 1 or type 2 diabetes, monitor blood sugar levels in people with diabetes, or assess how well diabetes treatments are working. It’s a key tool for preventing complications like nerve damage or kidney disease.

What Does the Test Involve?

A small blood sample is taken from your arm, usually by a nurse or phlebotomist. The sample is then analyzed using a specialized HPLC machine to measure the percentage of hemoglobin that is coated with sugar.

What Do the Results Mean?

Results are reported as a percentage, indicating the proportion of hemoglobin molecules linked to glucose. While reference ranges vary by lab, higher percentages generally suggest higher average blood sugar levels, which may indicate poor diabetes control.

Common Causes of Abnormal Results

Elevated HbA1c levels can result from poorly controlled diabetes, certain medications (like steroids), or conditions that affect red blood cell lifespan (e.g., anemia). Low levels may occur in people with very low blood sugar or certain genetic conditions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

HbA1c

Frequently asked questions

What factors might affect my HbA1c results?
Several factors can influence HbA1c, including recent blood sugar fluctuations, pregnancy, certain medications (like birth control pills or blood thinners), and conditions that shorten red blood cell life (e.g., hemolytic anemia). It’s important to discuss these with your doctor.
How often should I get this test?
For people with diabetes, HbA1c testing is typically recommended every 3 to 6 months to track progress and adjust treatment plans. Your doctor will determine the frequency based on your specific needs and health status.
Can diet or exercise change my HbA1c results?
Yes, lifestyle changes like diet and exercise can significantly impact HbA1c levels. Improving these habits often leads to better blood sugar control, reflected in lower HbA1c percentages over time.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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