Therefore, our primary objective to conduct a prospective, cross-sectional study to investigate the prevalence of thiamin deficiency in a large group of ambulatory patients with heart failure using High-Performance Liquid Chromatography (HPLC). This method has many advantages including its high level of recovery (102% on average), high intra- and inter-day precisions within 5-9%, as well as having a considerably low elution time of 15 min.