Liothyronine is used to treat an underactive thyroid (hypothyroidism). It replaces or provides more thyroid hormone, which is normally made by the thyroid gland. Liothyronine is a man-made form of thyroid hormone. Low thyroid hormone levels can occur naturally or when the thyroid gland is injured by radiation/medications or removed by surgery. Having enough thyroid hormone helps you stay healthy. For children, having enough thyroid hormone helps them grow and learn normally.

This medication is also used to treat other types of thyroid problems (such as certain types of goiters, thyroid cancer). It can also be used to test for certain types of thyroid disease.

This medication should not be used to treat infertility unless it is caused by low thyroid hormone levels.

Take this medication by mouth with or without food as directed by your doctor, usually once daily. It is best to take it at the same time each day so your thyroid hormone level is kept at a constant level.

Take this medication regularly to get the most benefit from it. Do not stop taking it without first talking with your doctor. Thyroid replacement treatment is usually taken for life.

The dosage is based on your medical condition, age, lab test results, and response to treatment.

Certain medications can decrease the absorption of liothyronine. Examples include products that contain aluminum or magnesium, antacids, sucralfate, calcium supplements, iron, bile acid-binding resins (such as cholestyramine, colestipol, colesevelam), simethicone, sevelamer, sodium polystyrene sulfonate, among others. If you take any of these medications, take them at least 4 hours before or after liothyronine. If you take lanthanum, take it at least 2 hours before or after liothyronine.

Symptoms of low thyroid hormone levels include tiredness, muscle aches, constipation, dry skin, weight gain, slow heartbeat, or sensitivity to cold. You may see an improvement in these symptoms within a few days. Tell your doctor if you do not get better or if you get worse.

Temporary hair loss may occur during the first few months of starting this drug, especially in children. If this effect lasts or gets worse, tell your doctor or pharmacist promptly.

Remember that this medication has been prescribed because your doctor 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.

Though unlikely, it is possible to have too much thyroid hormone. Tell your doctor right away if you have symptoms of too much thyroid hormone, including:

• headache
• mental/mood changes (such as irritability, nervousness)
• increased sweating
• sensitivity to heat
• diarrhea
• menstrual changes

Get medical help right away if you have any very serious symptoms of too much thyroid hormone, including:

• chest pain
• fast/pounding/irregular heartbeat
• swelling ankles/feet
• trouble breathing
• unusual tiredness

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe 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 or at www.fda.gov/medwatch.

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 liothyronine, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• decreased adrenal gland function
• heart disease (such as chest pain, heart failure, irregular heartbeat, heart attack)
• high blood pressure
• diabetes
• water diabetes (diabetes insipidus)

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

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

Liothyronine passes into breast milk but is unlikely to harm a nursing infant. Consult your doctor before breastfeeding.

See also How to Use section.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669. Symptoms of overdose may include: fast/irregular heartbeat, chest pain, trouble breathing, confusion.

Do not share this medication with others.

Lab and/or medical tests (such as thyroid function) should be done while you are taking this medication. Keep all medical and lab appointments.

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. Take your next dose at the regular time. Do not double the dose to catch up unless your doctor instructs you to do so. Call your doctor if you miss 2 or more doses in a row. Ask your doctor ahead of time what to do about a missed dose and follow your doctor's specific directions.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications 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.