In our research, Spirulina produced in Turkey has a high antioxidant capacity that changes between 1.281 and 7.110 mg GAE/100 g and determined by the three common methods (ABTS, CUPRAC, and DPPH). The major phenolics found in Spirulina were acacetin (53.62%) and pinocembrin (41.28%). The bio-accessibility values of the phenolic compounds in Spirulina were approximately 60%. PUFA’s are the significant antioxidant compounds to prevent lipid peroxidation. S. platensis has been found to reduce blood sugar and oxidative stress due probably to the high amount of omega-6 PUFA. Antioxidant enzyme levels of GSH-Px and SOD were increased 140% and 59% in the healthy rats treated with Spirulina and the diabetics treated with Spirulina. In diabetic rats fed with Spirulina, glucose, triglyceride, total cholesterol levels in blood and malondialdehyde content in body tissues were decreased by 20, 31, 22 and up to 56%, respectively.