The article gives an overview of the circumstances-eating habits, disorders of absorption in the intestinal and other disease, certain drugs and substances occurring in nature affecting the metabolism of thyroid hormones on many levels, thyroid disruptors, for which compensation may be healing broken thyroid function to be unsatisfactory in spite of following the rules of substitution treatment. Knowledge of these conditions and adapting to them timely by adjusting either the eating habits or thyroid hormone by adjusting benefits, allowing the patient to improve his subjective feelings from treatment and improving compliance.Key words: absorption - biological availability - compliance - levothyroxine therapy - drug interactions - nutritional habits - thyroid disruptors.