Skip to content

Hemoglobin A1c (HbA1c) with mass fraction measurement 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 helps track long-term blood sugar control, useful for diabetes management."]

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

Key facts at a glance

LOINC
31156-3
Short code
Hgb Barts MFr Bld
Synonyms
Hgb Barts 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 is HbA1c important?

Unlike daily blood sugar checks, HbA1c gives a broader picture of how well your body manages glucose over time. It’s a key tool for doctors to assess diabetes control and adjust treatment plans if needed.

How is this test done?

A small blood sample is taken from your arm, usually from a vein in your arm or hand. The sample is then processed to measure the percentage of hemoglobin molecules that are coated with glucose.

What does a high or low HbA1c mean?

Elevated HbA1c levels may indicate poor blood sugar control, which could be linked to diabetes or other metabolic conditions. Lower-than-normal levels might suggest very good control, but this isn’t always the case and should be discussed with your healthcare provider.

What can affect HbA1c results?

Factors like recent blood loss, severe illness, pregnancy, or certain medications can temporarily affect HbA1c levels. Smoking, anemia, or kidney disease may also influence results.

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?
Your doctor will determine how often you need HbA1c testing based on your health status, diabetes management plan, and other factors. Regular testing is common for people with diabetes to track progress.
Does HbA1c test show immediate blood sugar spikes?
No, HbA1c reflects average blood sugar levels over months, not short-term spikes. It doesn’t capture sudden changes like those from meals or exercise.
Can HbA1c be affected by diet?
While diet influences blood sugar, HbA1c measures long-term glucose exposure in red blood cells. Short-term dietary changes won’t immediately alter the result, but long-term dietary habits can impact overall levels.
  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