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Hemoglobin A1c (Glycated Hemoglobin) Mass Fraction

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

This test measures the percentage of hemoglobin in your blood that has sugar (glucose) attached to it. It reflects 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
4547-6
Short code
Hgb A1 MFr Bld
Synonyms
Hgb A1 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

What This Test Measures

HbA1c is a form of hemoglobin that has glucose molecules bound to it. It’s a stable protein in red blood cells and provides a snapshot of your blood sugar levels over time, accounting for factors like red blood cell lifespan.

Why It’s Done

Doctors order HbA1c tests to diagnose diabetes, monitor diabetes treatment progress, or assess risk for complications like nerve damage or heart disease in people with prediabetes or diabetes.

How It’s Performed

A small blood sample is taken from your arm. The test measures the proportion of hemoglobin molecules with attached glucose, typically reported as a percentage.

What to Expect Before or After

No special preparation is needed, but fasting isn’t required. Results may take a few days to return, depending on your lab’s processing 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.

HbA1c is critical for diagnosing diabetes (typically ≥6.5%) and guiding treatment. Lower-than-normal levels (below 5.7%) may indicate good blood sugar control, while higher levels suggest poor management and increased risk of complications.

Short name

HbA1c

Frequently asked questions

How often should I get an HbA1c test?
Typically, people with diabetes get tested every 3–6 months, while those with prediabetes may need testing every 1–2 years unless advised otherwise.
Can HbA1c be affected by other health conditions?
Yes, conditions like anemia, kidney disease, or certain medications (e.g., retinoids) can alter HbA1c levels. Your doctor may adjust interpretation if these factors apply to you.
Does diet or exercise impact HbA1c results?
While diet and exercise influence blood sugar levels, they don’t directly change HbA1c. However, improving these habits can help lower your HbA1c 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