Synthroid is an inactive T4 that requires conversion to active T3 in your tissues. If you have inflammation, gut issues, genetics that limit conversion enzymes, or endocrine-disrupting chemical exposure, this conversion fails and you remain hypothyroid despite normal labs. 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]. Find patient medical information for Levothyroxine (Levoxyl, Synthroid, Tirosint,and others) on WebMD including its uses, side effects and safety, interactions, pictures, warnings, and user. 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). Synthroid (levothyroxine) is a synthetic thyroid hormone used to treat hypothyroidism and manage thyroid cancer alongside surgery and radioiodine therapy. It replaces missing thyroxine when the body cannot produce enough naturally. Synthroid is a thyroid medicine that replaces a hormone normally produced by your thyroid gland to regulate the body's energy and metabolism. Synthroid is a prescription medicine used to treat hypothyroidism (low thyroid hormone). Synthroid is a prescription medicine used to treat the symptoms of hypothyroidism and an enlarged thyroid gland (goiter). Learn about dosage, side effects, drug interactions, warnings, and more. Take Synthroid once a day, every day, at the same time before breakfast. Only take Synthroid with water and on an empty stomach. Wait 30 minutes to 1 hour before eating or drinking anything other than water. Keep this cheat sheet handy for fast facts about Synthroid and how to take it the right way. Synthroid (levothyroxine) is a brand-name prescription drug that’s used to treat hypothyroidism and suppress TSH. Learn about side effects, dosage, and more. SYNTHROID® (levothyroxine sodium) tablets, for oral use is a prescription, man-made thyroid hormone that is used to treat a condition called hypothyroidism in adults and children, including infants.