Synthroid

Generic name:levothyroxine [ LEE-voe-thye-ROX-een ]
Drug class:Thyroid drugs

Medically reviewed by Philip Thornton, DipPharm. Last updated on May 3, 2022.

What is Synthroid?

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). Levothyroxine is given when your thyroid does not produce enough of this hormone on its own.

Synthroid is also used in patients who need surgery and radioiodine therapy to manage a type of thyroid cancer called well-differentiated thyroid cancer.

Warnings

You may not be able to take Synthroid if you have certain medical conditions. Tell your doctor if you have an untreated or uncontrolled adrenal gland disorder, a thyroid disorder called thyrotoxicosis, or if you have any recent or current symptoms of a heart attack.

Before taking this medicine

Synthroid should not be used to treat obesity or weight problems. Dangerous side effects or death can occur from the misuse of levothyroxine, especially if you are taking any other weight-loss medications or appetite suppressants.

Since thyroid hormone occurs naturally in the body, almost anyone can take levothyroxine. However, you may not be able to take this medicine if you have certain medical conditions. Tell your doctor if you have:

• an untreated or uncontrolled adrenal gland disorder;

• a thyroid disorder called thyrotoxicosis; or

• symptoms of a heart attack (chest pain or heavy feeling, pain spreading to the jaw or shoulder, nausea, sweating, general ill feeling).

To make sure Synthroid is safe for you, tell your doctor if...