Objective: Taking levothyroxine (L-T 4 ) with coffee or with water followed by coffee intake within a few minutes results in poor TSH response in many patients. T 4 is available in tablet form worldwide, but novel formulations in soft gel capsule or liquid form are now available. Design: We fortuitously identified a euthyroid patient who wrongly consumed liquid L-T 4 with coffee at breakfast; after changing the time of consumption to 30 min before breakfast, no change in TSH, free T 4 (fT 4 ), and free tri-iodothyronine (fT 3 ) concentrations was observed. Once the first patient was identified, additional stable euthyroid patients who consumed liquid L-T 4 with coffee were identified. Methods: Patients were recruited by searching our 'thyroid patients' database. All the patients on liquid L-T 4 treatment were contacted by phone to ask them whether they took L-T 4 at breakfast. We identified 54 patients who were submitted to TSH, fT 4 , and fT 3 evaluation, with the indication that the same dosage of L-T 4 be consumed 30 min before breakfast. We determined their TSH, fT 4 , and fT 3 concentrations after 3 and 6 months again.