Hemoglobin A2 is a type of hemoglobin in the human body. After birth, the human body has three main components of hemoglobin: the first, hemoglobin A, is the most dominant hemoglobin in adults, accounting for more than 95% of all hemoglobin. The second, hemoglobin A2, accounts for 2-3% of all hemoglobin. The third, hemoglobin F, accounts for about 1% of all hemoglobin. Human hemoglobin is a binding protein composed of hemoglobin and pearlin, and pearlin consists of two kinds of peptide chains: one is alpha peptide chain; the other is non-alpha peptide chain. An increase in hemoglobin A2 often indicates a decrease in the number of beta peptide chains in the body, a condition commonly seen in patients with beta thalassemia. If there is a significant increase in hemoglobin A2, the diagnosis of beta thalassemia is basically confirmed.