Background: ω-3 fatty acids in seafood, fatty fish, and supplements have health benefits as their variable physiological benefits. Aims: This study aimed to investigate the effects of different doses of ω-3 fatty acids on body weight, levels of thyroid hormones, lipid components, oxidative markers and complete blood count (CBC). Materials and Methods: Mice (n=160) were divided into 8 groups for short and long treatments. Results: Data showed that oral treatment reduced the body weight of mice organs in a dose and time-dependent manner. The treatments also reduced serum cholesterol and triglycerides levels as well as GSH. In contrast, the treatment increased the serum levels of anti-oxidants such as GPx, SOD and MDA. Meanwhile, the treatments increased significantly the serum levels of both T₃ & T₄ and decreased the pituitary TSH. The treatment also increased RBCs and platelet counts, as well as the hemoglobin concentration. All recorded effects of ω-3 fatty acids were in a dose and time-dependent manner. Conclusion: Intake of ω-3 fatty acids decreases obesity and amends animea through reducing increasing oxidative stress and enhancing RBCs and hemoglobin biosynthesis.