This medication should not be used either alone or in combination with diet pills to treat obesity or for weight loss because serious, even life-threatening, effects could occur. Large doses of this medication, especially with diet pills, may cause symptoms of toxicity. See the Side Effects and Overdose sections for more information.

Levothyroxine is used to treat an underactive thyroid (hypothyroidism). It replaces the hormone that is normally produced by the thyroid gland. Low thyroid levels can occur naturally or when the thyroid gland is injured by radiation/medications or removed by surgery. It is important to have adequate levels of thyroid hormone in your bloodstream to maintain normal mental and physical activity. In children, adequate levels of thyroid hormone are important for normal mental and physical growth and development.

This medication is used to treat other types of thyroid disorders as well (e.g., certain types of goiters, thyroid nodules, thyroiditis, thyroid cancer).

Take this medication by mouth usually once a day on an empty stomach, 1/2 to 1 hour before breakfast, or as directed by your doctor. To prevent difficulty swallowing the tablet, take it with a full glass of water unless otherwise directed by your doctor.

For children who cannot swallow whole tablets, crush the tablet and mix in 1 or 2 teaspoons (5 or 10 milliliters) of water, and give using a spoon or dropper as soon as possible after preparation. Do not store the mixture for later use. Do not mix crushed tablets in soybean infant formula. Consult your pharmacist for more information.

Use this medication regularly in order to get the most benefit from it. Remember to use it at the same time each day. Your doctor may need to adjust your dosage based on your medical condition, your response to therapy, and your laboratory test results.

Do not stop taking this medication without consulting with your doctor. Replacement therapy is usually taken for life.

It may take up to 4-6 weeks before the full benefits of this medication take effect. Inform your doctor if your condition persists or worsens.

Symptoms of low thyroid levels include fatigue, muscle aches, constipation, dry skin, weight gain, slow heart rate, sensitivity to cold, or dry brittle hair that tends to fall out easily. These symptoms should disappear as your body adjusts to the medication. If they persist or become bothersome, notify your doctor promptly.

Headache, nervousness, trembling, sweating, increased appetite, diarrhea, weight loss or insomnia may occur. If any of these effects persist or worsen, notify your doctor promptly.

In rare instances, some hair loss may occur during the first few months of starting this drug. This effect is usually temporary as your body adjusts to this medication. If this effect persists or worsens, notify your doctor promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Seek immediate medical attention if you have any of these very unlikely but serious side effects: chest pain, rapid or irregular heartbeat, shortness of breath, seizures.

An allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of an allergic reaction include: rash, itching/swelling (especially of the face/tongue/throat), dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking levothyroxine, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies.

This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you have: overactive thyroid conditions (e.g., thyrotoxicosis), a heart attack (acute myocardial infarction), adrenal gland problems (e.g., uncorrected adrenal insufficiency).

Do not use thyroid drugs for weight control.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: heart problems (e.g., hypertension, congestive heart failure, arrhythmias, coronary artery disease), diabetes, male or female infertility problems (unless caused by underactive thyroid disease), bone loss disease (e.g., osteoporosis), other hormone disorders (e.g., hypothalamic/pituitary hormone deficiencies, autoimmune polyglandular syndrome), certain thyroid problems (e.g., nontoxic diffuse goiter, nodular thyroid disease), blood clotting disorders.

Notify your doctor or dentist that you are taking this medication prior to any surgery.

Caution is advised when using this drug in children because overuse may reduce the child's future adult height. Consult your doctor for details.

Caution is advised when using this drug in the elderly because they may be more sensitive to the effects of the drug.

Current information shows that this drug may be used during pregnancy. Tell your doctor if you are pregnant because your dose will have to be adjusted.

Small amounts of this drug pass into breast milk. Consult your doctor before breast-feeding.

Your healthcare professionals (e.g., doctor or pharmacist) may already be aware of any possible drug interactions and may be monitoring you for it. Do not start, stop or change the dosage of any medicine before checking with them first.

Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription drugs you may use, especially of: warfarin, digoxin, estrogen products (including estrogen-containing birth control pills), diabetes medicines (e.g., insulin, glipizide, rosiglitazone), amiodarone, iodide (including radiographic contrast agents containing iodine), lithium, anti-thyroid agents (e.g., methimazole, propylthiouracil), androgens/anabolic steroids, glucocorticoids (e.g., dexamethasone, prednisone), high dose salicylates (e.g., aspirin), phenobarbital, rifamycins (e.g., rifampin), beta blockers (e.g., propranolol), antidepressants (e.g., amitriptyline, maprotiline, sertraline), cytokines (e.g., interferon-alpha, interleukin-2), growth hormones, ketamine, theophylline.

Check the labels on all your medicines (e.g., cough-and-cold products, diet aids) because they may contain ingredients such as decongestants or caffeine that could increase your heart rate or blood pressure. Ask your pharmacist about the safe use of these products.

Certain medicines may decrease absorption of this drug into your bloodstream. Therefore, take levothyroxine 4 hours apart from: calcium supplements, iron supplements, antacids, simethicone, orlistat, cholestyramine, colesevelam, colestipol, sucralfate, sodium polystyrene sulfonate.

Certain foods may decrease absorption of this medication when taken at the same time. Take levothyroxine separately from: soybean flour (soybean infant formula), walnuts, dietary fiber.

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.

If overdose is suspected, contact your local poison control center or emergency room immediately. US residents can call the US national poison hotline at 1-800-222-1222. Canadian residents should call their local poison control center directly. Symptoms of overdose may include: excessive sweating, extreme nervousness, fast/irregular heartbeat, chest pain, seizures.

Laboratory and/or medical tests (e.g., thyroid function tests) should be done periodically to monitor the effectiveness of this medication. Inform your doctor if you change to a different brand of thyroid hormone.

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up. Call your doctor if you miss 2 or more doses in a row.

Store at room temperature (77 degrees F or 25 degrees C) away from light and moisture. Brief storage between 59 and 86 degrees F (15 and 30 degrees C) is permitted. Do not store in the bathroom. Keep all medicines away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details about how to safely discard your product.

Information last revised October 2008 Copyright(c) 2008 First DataBank, Inc.