Previous studies have demonstrated that hemoglobin-haptoglobin (Hb-Hp) complex plays a role in developing vascular complications in type 2 diabetes mellitus (T2DM). The complexes bind with Apolipoprotein A1 (ApoA1) of high-density lipoprotein (HDL), affecting the function of Lecithin:Cholesterol Acyltransferase (LCAT), and impairing the reverse cholesterol transport mechanism (RCT). This study investigated the influence of Hp phenotypes on serum levels of ApoA1 and LCAT in patients with T2DM.