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Hemoglobin A1c (HbA1c) by High-Performance Liquid Chromatography (HPLC)

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

This test measures the percentage of hemoglobin that is coated with sugar, reflecting your average blood sugar levels over the past 2–3 months.

Quick summary

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

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

Key facts at a glance

LOINC
55372-7
Short code
Hgb CSp MFr Bld
Synonyms
Hgb CSp MFr Bld
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

Why This Test Matters for Blood Sugar Control

Unlike daily blood sugar checks, HbA1c gives a broader picture of how well your blood sugar has been managed over time. It’s a key tool for diagnosing diabetes and assessing treatment effectiveness.

How the Test Works

Blood is drawn and analyzed using high-performance liquid chromatography (HPLC), which separates hemoglobin types based on their sugar content. The test measures the proportion of hemoglobin linked to glucose (HbA1c).

What to Expect Before the Test

No special preparation is needed, but fasting is not required. Wear comfortable clothing and bring any medications you’re currently taking. Avoid smoking or chewing gum 30 minutes before the draw.

What the Results Mean

Results are typically reported as a percentage (e.g., 5.7%–6.4% may indicate prediabetes or poor control). While reference ranges vary by lab, higher percentages often signal higher average blood sugar levels over time.

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

How often should I get this test?
For most people with diabetes, HbA1c is checked every 3–6 months. Your doctor may adjust frequency based on your blood sugar goals and overall health.
What affects my HbA1c results?
Several factors can influence results, including recent blood sugar spikes, illnesses (e.g., infections), pregnancy, or certain medications (e.g., steroids). Always discuss any changes with your healthcare provider.
Can I fast before this test?
No, fasting is not required for HbA1c. Unlike some other blood tests, it measures average sugar levels over time, not immediate readings.
  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