In this study, the level of serum lipid peroxidation (Malondialdehyde: MDA), serum antioxidants (reduced glutathione: GSH, superoxide dismutase: SOD, catalase: CAT), antioxidant vitamins (Vitamins C and E) and some serum antioxidant elements (zinc: Zn, copper: Cu, selenium: Se, and iron: Fe) in patients with diabetes, hypertension and both hypertension/diabetes at various age range was investigated along with that of healthy adults at same age range in order to ascertain the effect of age changes on the antioxidant. The gene discussed is CAT; the disease is hypertensive disorder.