Levothyroxine is a replacement for a hormone 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). It is also used to treat or prevent goiter (enlarged thyroid gland), which can be caused by hormone imbalances, radiation treatment, surgery, or cancer.
Important information
You may not be able to take levothyroxine 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.
Levothyroxine 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.
Before taking this medicine
Levothyroxine 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 medication if you have certain medical conditions.
To make sure levothyroxine is safe for you, tell your doctor if you have:
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a thyroid disorder called thyrotoxicosis;
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heart disease, coronary artery disease, or a history of blood clots;
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diabetes (insulin or oral diabetes medication doses may need to be changed when you start taking levothyroxine);
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anemia (lack of red blood cells);
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osteoporosis, or low bone mineral density;
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problems with your pituitary gland;
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any food or drug allergies;
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an untreated or uncontrolled adrenal gland disorder; or
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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 jaw or shoulder, nausea, sweating, general ill feeling).
Tell your doctor if you have recently received radiation therapy with iodine (such as I-131).
FDA pregnancy category A. Levothyroxine is not expected to harm an unborn baby. If you become pregnant while taking this medicine, 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.
See also: Pregnancy and breastfeeding warnings (in more detail)
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.
How should I take levothyroxine?
Take levothyroxine exactly as prescribed by your doctor. Follow all directions on your prescription label. Your doctor may occasionally change your dose to make sure you get the best results. Do not take this medicine in larger or smaller amounts or for longer than recommended.
Do not share this medication with another person, even if they have the same symptoms you have.
Levothyroxine works best if you take it on an empty stomach, at least 30 minutes before breakfast. Follow your doctor"s dosing instructions and try to take the medicine at the same time each day.
It is very important to take Levoxyl with a full glass (8 ounces) of water. The Levoxyl tablet can dissolve very quickly and swell in the throat, possibly causing choking or gagging.
While using levothyroxine, you may need frequent medical tests.
Tell any doctor or dentist who treats you that you are using levothyroxine.
Store at room temperature away from moisture and heat.
It may take several weeks before your body starts to respond to levothyroxine. Keep using this medicine even if you feel well. You may need to use this medicine for the rest of your life to replace the thyroid hormone your body cannot produce.
What happens if I miss a dose?
Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.
Overdose symptoms may include headache, leg cramps, tremors, feeling nervous or irritable, chest pain, shortness of breath, and fast or pounding heartbeats.
What should I avoid?
Certain medicines can make levothyroxine less effective if taken at the same time. If you use any of the following drugs, avoid taking them within 4 hours before or 4 hours after you take levothyroxine:
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calcium carbonate (Alka-Mints, Calcium Oyster Shell, Caltrate, Os-Cal, Oyster Shell Calcium, Rolaids Soft Chew, Tums, and others);
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cholestyramine, colestipol;
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ferrous sulfate iron supplement;
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sucralfate;
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sodium polystyrene sulfonate (Kalexate, Kayexalate, Kionex); or
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antacids that contain aluminum or magnesium - Acid Gone, Gaviscon, Maalox, Milk of Magnesia, Mintox, Mylanta, Pepcid Complete, and others).
Avoid the following food products, which can make your body absorb less levothyroxine: infant soy formula, cotton seed meal, walnuts, and high-fiber foods.
Levothyroxine side effects
Get emergency medical help if you have any of these signs of an allergic reaction to levothyroxine: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have a serious side effect such as:
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fast or irregular heart rate;
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fever, hot flashes, sweating;
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sleep problems (insomnia);
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changes in your menstrual periods; or
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vomiting, diarrhea, appetite changes, weight changes.
Common levothyroxine side effects may include mild hair loss.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
See also: Side effects (in more detail)
What other drugs will affect levothyroxine?
Many other medicines can be affected by your thyroid hormone levels. Other medicine may also increase or decrease the effects of levothyroxine.
Many drugs can interact with levothyroxine and not all possible interactions are listed in this medication guide.
Tell your doctor about all medications you use, start using, or stop using during your treatment with this medicine. This includes prescription, over-the-counter, vitamin, and herbal products. Give a list of all your medicines to any healthcare provider who treats you.
