Skip to content

Hemoglobin A2 Fraction (Mass Fraction)

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

This test measures the percentage of a specific type of hemoglobin (HbA2) in your blood, which is a component of healthy red blood cells.

Quick summary

["HbA2 helps assess how well your body produces normal hemoglobin over time."]

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

Key facts at a glance

LOINC
4551-8
Short code
Hgb A2 MFr Bld
Synonyms
Hgb A2 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 Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms or risk factors for conditions like thalassemia, sickle cell disease, or diabetes. It’s also used to monitor hemoglobin production in people with certain blood disorders or genetic conditions.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm or hand to draw a blood sample. The process is quick and usually causes only mild discomfort.

What the Results Mean

HbA2 levels are typically expressed as a percentage of total hemoglobin. Higher levels may indicate certain blood disorders, while lower levels could suggest conditions affecting hemoglobin production.

Common Conditions Monitored

This test is often used to diagnose or monitor thalassemia (a group of blood disorders), sickle cell trait or disease, and other inherited blood conditions. It can also help track hemoglobin stability in people with diabetes or other chronic health issues.

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

HbA2

Frequently asked questions

What does an abnormal HbA2 result mean?
An abnormal result may signal a genetic blood disorder like thalassemia or sickle cell trait. Your doctor will discuss your results and next steps based on your symptoms and medical history.
How often should I get this test?
Your doctor will determine the frequency based on your condition. Some people with inherited blood disorders may need testing every few months or annually, while others may only need it occasionally.
Is there anything I should avoid before the test?
Avoid heavy meals or strenuous activity 1–2 hours before the test, but no other restrictions apply. Drink water as usual unless instructed otherwise.
  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