Although the healthcare field is increasingly aware of the importance of free radicals and oxidative stress, screening and monitoring has yet become a routine test since, dangerously, there are no symptoms of this condition. Therefore, in very few cases is oxidative stress addressed. Paradoxically, patients are often advised supplementation with antioxidants and or diets with increased antioxidant profile, which range from vitamins to minerals which is action against oxidative stress states and even more so no test is advised to assess whether the patient is under attack by free radicals or has a depleted antioxidant capacity. Hence oxidative stress is an imbalance between free radicals (ROS, Reactive Oxygen Species) production and existing antioxidant capacity (AC), living organisms have a complex anti-oxidant power. A decrease in ROS formation is often due to an increase in antioxidant capacity whilst an increase in the AC may be associated to decreased ROS values. But this is not always apparently so. Test kits for photometric determinations applicable to small laboratories are increasingly available.