Levothyroxine, also known as L-thyroxine, is a synthetic form of the thyroid hormone thyroxine (T 4). [4][7] It is used to treat thyroid hormone deficiency (hypothyroidism), including a severe form known as myxedema coma. [4] It may also be used to treat and prevent certain types of thyroid tumors. [4] It is not indicated for weight loss. [4] Levothyroxine is used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormone. This medicine is also used to help decrease the size of enlarged thyroid glands (also called a goiter). Levothyroxine is used to treat hypothyroidism (condition where the thyroid gland does not produce enough thyroid hormone). It is also used with surgery and radioactive iodine therapy to treat thyroid cancer. Levothyroxine oral tablets are used to treat hypothyroidism, goiter, and certain types of thyroid cancer. Learn about the drug's uses, interactions, and more. Here are 10 things you should know before taking levothyroxine, including what it’s for, side effects, brands, cost, and more. Levothyroxine is a man-made form of thyroxine (T4), one of the hormones your thyroid gland normally produces. It belongs to a class of medications called hormones, and it works by replacing thyroid hormone that your body is not making enough of. NHS medicines information on levothyroxine, including what it's used for, side effects, dosage and who can take it. Overview: Levothyroxine is used as a replacement hormone therapy for people with low thyroid hormone levels, among other uses. Levothyroxine interacts with many medicines and health conditions. Learn how symptoms of anxiety, diarrhea, and fatigue can be signs of taking too much levothyroxine for an underactive thyroid, and how to prevent it. Learn about the side effects of levothyroxine, from common to rare, for consumers and healthcare professionals.