What is levothyroxine?
Levothyroxine is a replacement for a hormone that is normally produced by your thyroid gland to regulate the body's energy and metabolism. Levothyroxine is given when the thyroid does not produce enough of this hormone on its own.
Levothyroxine treats hypothyroidism (low thyroid hormone). Levothyroxine is also used to treat or prevent goiter (enlarged thyroid gland), which can be caused by hormone imbalances, radiation treatment, surgery, or cancer.
Levothyroxine should not be used to treat obesity or weight problems.
Levothyroxine may also be used for purposes not listed in this medication guide.
What is the most important information I should know about levothyroxine?
Since thyroid hormone occurs naturally in the body, almost anyone can take levothyroxine. You should not use this medication if you have had a heart attack, a thyroid disorder called thyrotoxicosis, or an adrenal gland problem that is not controlled by treatment.
Before you take levothyroxine, tell your doctor if you have a serious thyroid disorder (thyrotoxicosis), heart disease, coronary artery disease, diabetes, anemia, problems with your pituitary or adrenal glands, a history of blood clots, if you have recently had a heart attack, or if you are having any symptoms of a heart attack (chest pain or heavy feeling, pain spreading to the arm or shoulder, nausea, sweating, general ill feeling).
If you use insulin or take diabetes medicine by mouth, ask your doctor if your dose needs to be changed when you start using levothyroxine.
Different brands of levothyroxine may not work the same. If you get a prescription refill and your new pills look different, talk with your pharmacist or doctor.
It may take several weeks before your body starts to respond to this medication. Do not stop taking the medicine suddenly. Even if you feel well, you may still need to take this medicine every day for the rest of your life to replace the thyroid hormone your body cannot produce.
Tell your doctor about all medications you use. This includes prescription, over-the-counter, vitamin, and herbal products. Do not start a new medication without telling your doctor. Keep a list of all your medicines and show it to any healthcare provider who treats you.
What should I discuss with my healthcare provider before taking levothyroxine?
Since thyroid hormone occurs naturally in the body, almost anyone can take levothyroxine. However, you may not be able to take this medication if you have certain medical conditions.
To make sure you can safely take levothyroxine, tell your doctor if you have:
a thyroid disorder called thyrotoxicosis;
heart disease, coronary artery disease, or a history of blood clots;
diabetes;
anemia (lack of red blood cells);
problems with your pituitary or adrenal glands;
an untreated or uncontrolled adrenal gland disorder; or
if you have recently had a heart attack, or are having any symptoms of a heart attack (chest pain or heavy feeling, pain spreading to the arm or shoulder, nausea, sweating, general ill feeling).
If you use insulin or take diabetes medicine by mouth, ask your doctor if your dose needs to be changed when you start using levothyroxine.
FDA pregnancy category A. Levothyroxine is not expected to harm an unborn baby. If you become pregnant while taking levothyroxine, do not stop taking the medicine without your doctor's advice. Having low thyroid hormone levels during pregnancy could harm both mother and baby. Your dose needs may be different during pregnancy.
Levothyroxine can pass into breast milk, but it is not expected to be harmful to a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby. Your dose needs may be different while you are nursing.
In most cases, you will need to take levothyroxine for the rest of your life. Taking levothyroxine over long periods of time may cause bone loss, which can lead to osteoporosis. Talk with your doctor about how this could affect you.