Metformin (MET) is today the most prescribed drug in the world for the treatment of type two diabetes, but also it is used as an anti-cancer agent and as a treatment for polycystic ovary syndrome. Due to its high consumption, low octanol-water partition coefficient (Kow -2.6), and high aqueous mobility, MET is expected to be present in surface waters once released in the environment through the wastewater effluent discharge. This study was conducted to evaluate the presence and behavior of antidiabetic compounds in urban wastewater treatment plants.