Thyroid hormones influence nearly every body organ. The current study planned to evaluate oxidative stress, biochemical and hematological parameters in hypothyroid dogs before and after treatment, and the antioxidant supplementation potency as an additional treatment to ordinary treatment, the involved dogs in the study were classified into 4 groups, apparently healthy group (10 euthyroid dogs) and 20 hypothyroid dogs, ten dogs were treated with ordinary therapy levothyroxine (treated 1), the other ten dogs by standard therapy with specific supplementation by zinc (treated 2) for 4 weeks. (TT4), (FT4), Catalase, Iron, Calcium, RBCS, Hb and HCT level in diseased dogs showed significant decrease when compared with other three groups. A significant increase in Zinc level was observed in treated 2 group when compared to pretreatment hypothyroidism group. TSH, phosphorus, Cholesterol, triglyceride, LDL, Glucose, ALT, AST and ALP were significantly increased in pretreatment hypothyroidism group compared with the other three groups. In treated groups, level of TT4, Catalase, RBCS, Hb and HCT were significantly increased compared with pretreatment group and there were no significant variations between the two post treatment groups.  FT4, Iron and Calcium in treated 2 group were significantly increased compared with pretreatment and treated 1 group. TSH, Cholesterol, triglyceride, LDL, glucose, ALT, ALP and AST were significantly decreased after both protocols of therapy compared with pretreatment group, but no significant differences were observed between the post treatment groups. Administration of zinc together with ordinary therapy can enhance the clinical recovery and can be suggested as a complementary therapy.