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Hemoglobin A2

Published: July 27, 2026Updated: August 25, 2026

Hemoglobin A2 (HbA2) is a minor component of hemoglobin in red blood cells, and its measurement is used to diagnose and monitor beta-thalassemia and other hemoglobinopathies.

Quick summary

HbA2 is a key diagnostic marker for beta-thalassemia.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 25, 2026Editorial policy

Key facts at a glance

Units
%
Clinical utility
diagnostic
Result kind
quantitative
FDA-cleared
Bio-Rad Hemoglobin A2, Trinity CAPILLARYS
interpretation: {"text":"Levels below 1.5% are uncommon and may indicate iron deficiency or alpha-thalassemia.","label":"Low HbA2"}; {"text":"Levels above 3.5% are indicative of beta-thalassemia trait and may require further genetic testing.","label":"High HbA2"}

Hemoglobin A2 (HbA2) is a hemoglobin variant that normally constitutes about 2-3% of the total hemoglobin in adult red blood cells. It is composed of two alpha and two delta chains.

Elevated levels of HbA2 are a hallmark of beta-thalassemia trait, where HbA2 levels are typically above 3.5%. This makes HbA2 measurement crucial for diagnosing the condition.

In addition to beta-thalassemia, abnormal HbA2 levels can also indicate other hemoglobinopathies, such as sickle cell anemia or hemoglobin E disease, making it a versatile diagnostic tool.

Frequently asked questions

What is a normal HbA2 level?
The normal range for HbA2 is between 1.5% and 3.5% of the total hemoglobin.
How is HbA2 measured?
HbA2 is typically measured using high-performance liquid chromatography (HPLC) or capillary electrophoresis.
  1. 1
    National Institutes of Health: ThalassemiaSource
  2. 2
    Mayo Clinic: HemoglobinopathiesSource

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

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Medically reviewed by WellAlly Editorial Team Last reviewed August 25, 2026. · Read our editorial policy