Background & Aim: This study was designed to evaluate the therapeutic effect of Allium cepa on the atherogenic, serum biochemical, and hematologic indices in Wistar rats administered KBrO3.Experimental: Forty male rats assigned into 8 groups (n=5) in which groups A, B, C, D, and E received distilled water (2 mL), KBrO3 (50 mg/kg), quercetin 70 mg/kg, aqueous extract of Allium cepa (AEAC) at 150 mg/kg and 300 mg/kg, respectively. Groups F, G, and H received KBrO3 with AEAC at 150 mg/kg, 300 mg/kg, and quercetin, respectively, on alternate days for 3 months.Results: The phytochemical analysis of the AEAC revealed the presence and absence of some phytochemical constituents. The Acute toxicity result indicated that AEAC has an LD50 above 5000mg/kg. KBrO3 caused a significant (P<0.05) decrease in the haematological parameters relative to the control but administration of KBrO3 with AEAC or quercetin improved the parameters. KBrO3 caused a significant (P<0.05) increase in the levels of triglycerides (TG), total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C), but significantly (P<0.05) lower level of HDL-C. Treatment with KBrO3 and AEAC or quercetin significantly (P<0.05) abrogated these KBrO3-induced alterations. Similar ameliorative effects of AEAC were found in KBrO3-induced alterations in atherogenic indices, such as Castelli's Risk Index I (CRI-1), Castelli's Risk Index II (CRI-II), Atherogenic Coefficient (AC), and Atherogenic Index of Plasma (AIP) indices relative to the control.Recommended applications/industries: According to the present results, AEAC showed amelioration against KBrO3-induced derangement in the haematological, lipid, and atherogenic indices and it might be helpful in the management of cardiovascular problems. تفاصيل المقالة