Diabetes mellitus medications	May increase dosing of diabetes medications needed to achieve glycemic control
Digitalis	May decrease serum digitalis levels
Foods	Patients who regularly consume walnuts, dietary fiber, soybean flour, cottonseed meal, or grapefruit juice may need higher doses of levothyroxine
Ketamine	Concurrent use may result in significant hypertension and tachycardia
Oral anticoagulants	May increase effects
Selective serotonin reuptake inhibitors	May increase therapeutic and toxic effects
Sympathomimetics	Concurrent use may increase risk of a cardiac event in patients with coronary artery disease
Tricyclic antidepressants	May increase therapeutic and toxic effects
Tyrosine kinase inhibitors	Concurrent use may result in hypothyroidism