What causes foul, strong smelling urine? I have noticed this since starting to take levothyroxine a couple months ago. I drink 4 to 5 glasses of water a day and have for several years. Have not had this problem until around the time I was prescribed levothyroxine for diagnosis of borderline hypothyroid. Have no other changes I can think of. Have had a urine sample taken around the same time I started taking the prescription as well as a blood test 3 months after starting levothyroxine. No problems were found and my thyroid is within normal range. Thanks for advice.