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Hemoglobin A1c (HbA1c) measured in serum/plasma by high-performance liquid chromatography (HPLC)

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

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

Quick summary

["HbA1c helps 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
63265-3
Short code
ENA Jo1 Ab Fld Ql ID
Synonyms
ENA Jo1 Ab Fld Ql ID
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
immune-diffusion
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 HbA1c Matters for Diabetes Care

HbA1c provides a snapshot of your blood sugar levels over time, which isn’t possible with a single blood sugar test. It’s a key tool for doctors to assess whether your diabetes treatment is working effectively and to adjust your care plan as needed.

How HbA1c Works in Your Body

Hemoglobin, the protein in red blood cells that carries oxygen, naturally binds to sugar molecules in your blood. Over time, this creates glycated hemoglobin (HbA1c). The percentage of your total hemoglobin that is glycated reflects your average blood sugar levels during the production of red blood cells (about 2–3 months).

What Normal Results Mean

While specific reference ranges vary by lab, HbA1c results are often interpreted as follows: lower-than-normal levels may indicate good blood sugar control, while higher-than-normal levels suggest poor control and may prompt further medical evaluation.

How HbA1c Is Different from Daily Blood Sugar Tests

Unlike fingerstick blood sugar tests (e.g., fasting glucose or random glucose), HbA1c doesn’t depend on when you last ate or drank. It’s a stable measure of long-term blood sugar trends, making it ideal for monitoring chronic conditions like diabetes.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance of HbA1c Results

Short name

HbA1c

Frequently asked questions

How often should I get an HbA1c test?
Typically, people with diabetes are advised to get an HbA1c test every 3–6 months to track progress and adjust treatments. Your doctor may recommend more frequent testing if your blood sugar is unstable or if you’re making significant lifestyle changes.
Can HbA1c results change if I’ve recently had a blood donation?
Yes, HbA1c can be affected by recent blood donation, as it measures hemoglobin levels from your red blood cells. If you donated blood within the past few months, your doctor may request a repeat test or use a different reference period for interpretation.
What does an HbA1c test require before the procedure?
No special preparation is needed for an HbA1c test. You can eat and drink normally, but fasting is not required. The test is typically done by drawing a small blood sample from your arm, similar to other blood tests.
  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