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Hemoglobin A1c (HbA1c) measured by high-performance liquid chromatography (HPLC)

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

This test measures the average level of blood sugar (glucose) over the past 2–3 months by examining your red blood cells.

Quick summary

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

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

Key facts at a glance

LOINC
30350-3
Short code
Hgb BldV-mCnc
Synonyms
Hgb BldV-mCnc
Category
hematology
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Ref low
12
Ref high
17.5
Critical range
7 N/A – 20 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
85018
SNOMED
900000000000003004
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

What HbA1c Tests Measure

HbA1c is a form of hemoglobin (the protein in red blood cells that carries oxygen) that has been linked to glucose molecules. Over time, high blood sugar levels cause this attachment. The test quantifies this attachment to estimate your average blood sugar levels during the preceding 2–3 months, providing insight into how well your body manages glucose over time.

Why HbA1c Matters

Unlike daily blood sugar checks, HbA1c gives a broader picture of your glucose control. It’s particularly useful for diagnosing diabetes, monitoring treatment effectiveness, and identifying trends in blood sugar levels that might not be apparent from single measurements.

How HbA1c Is Performed

A small blood sample is taken from your arm, usually via a simple fingerstick. The sample is processed using HPLC to separate hemoglobin variants and measure the proportion of HbA1c. This method is highly accurate and standardized across labs.

What HbA1c Results Mean

Results are typically reported as a percentage (e.g., 5.7%, 6.5%, 7.8%). While specific ranges vary by lab, higher percentages generally indicate poorer glucose control. For example, a result above 6.5% may suggest diabetes, while lower values may indicate better control.

Reference range

Adult males: 13.5-17.5 g/dL; Females: 12.0-16.0 g/dLN/A

Specimen: whole-blood

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

Frequently asked questions

What does an abnormal HbA1c result mean?
An elevated HbA1c (typically ≥6.5%) often signals diabetes or prediabetes, prompting lifestyle changes or medication adjustments. Lower values (e.g., <5.7%) may indicate normal glucose metabolism, but repeated testing is advised if symptoms like fatigue or frequent urination persist.
How often should I get an HbA1c test?
If you have diabetes, HbA1c tests are usually recommended every 3–6 months to track progress. For those without diabetes but with risk factors (e.g., obesity, family history), annual testing may be advised. Your healthcare provider will determine the ideal frequency for you.
Can HbA1c test results change over time?
Yes, HbA1c levels can fluctuate due to diet, exercise, illness, or medication. Consistent trends (e.g., rising or falling over months) are more reliable than single measurements. Regular follow-ups help adjust treatment plans accordingly.
  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