Application of potentiometric electrodes in drug measurements, offer the advantages of speed and ease of preparation and procedures, relatively fast response, wide linear dynamic range, portability and low cost. The majority of drug sensors are based on ion pair complexes, to overcome the difficulties of synthesizing very differently shaped ionophores, which is an obligation caused by the very wide range of shapes of the drugs. The above-mentioned advantages are the result of the growing trend of development, and use of sensors in drug analysis. Levothyroxine, also L-thyroxine, synthetic T4, or 3,5,3’,5’-tetraiodo-L-thyronine, is a synthetic form of thyroxine (thyroid hormone). Levothyroxine is a replacement for a hormone that is normally produced by your thyroid gland to regulate the body's energy and metabolism. Levothyroxine is given when the thyroid does not produce enough of this hormone on its own. Observation of the patients who are used levothyroxine tablets but still have problem with their thyroid, leads to analysis the pharmaceutical formulation used for the first step. For this purpose, this research work introduces a novel levothyroxine potentiometric sensor for determination of levothyroxine in pharmaceutical formulation. This simple device can be easily used either by the pharmaceutical factories produce levothyroxine tablet in quality control unites or even by the physicians face to such patients. The proposed sensor shows a fast (~30 s), stable and Nernstian response (58.6±0.3 mV/decade) over a relatively wide levothyroxine concentration range of 1×10-5 to 1×10-2 mol L-1. Validation of the method shows suitability of the sensors for applies in the quality control analysis of levothyroxine in pharmaceutical formulation. Nothing to Disclose: FARF, EN-E, BL, PN, MRG