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. Simply switching from Synthroid to levothyroxine or levothyroxine so Synthroid may actually provide more stable serum thyroid levels in your body and therefore reduce your symptoms. 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. Synthroid (levothyroxine) is a brand-name prescription drug that’s used to treat hypothyroidism and suppress TSH. Learn about side effects, dosage, and more. For most patients, generic levothyroxine is clinically equivalent to Synthroid and far more affordable. Exceptions include patients needing tight TSH control (thyroid cancer, pregnancy) or those with absorption issues. Learn about Synthroid (levothyroxine) dosage, including starting doses, dosage charts for adults and children, adjustments, and how to take it safely. 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 prescription drug used to treat hypothyroidism and a certain kind of thyroid cancer. Learn about side effects and how to manage them.