SIDE EFFECTS: See also Precautions section. 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, tell your doctor or pharmacist 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. Though unlikely, it is possible to have too much thyroid hormone. Your doctor may need to reduce the dose of this medication. Tell your doctor right away if any of these unlikely but serious signs of too much thyroid hormone occur: headache, mental/mood changes (e.g., nervousness, irritability), shaking, sweating, sensitivity to heat, diarrhea, weight loss, trouble sleeping, tiredness, bone pain, easily broken bones. Get medical help right away if any of these rare but very serious side effects occur: chest pain, shortness of breath, fast/pounding/irregular heartbeat, swelling of the hands/feet, seizures. 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.

PRECAUTIONS: Before using levothyroxine, 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. This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you have: a certain overactive thyroid condition (thyrotoxicosis), a recent heart attack (acute myocardial infarction), adrenal gland problem (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., angina, heart failure, irregular heartbeat), high blood pressure, diabetes (diabetes mellitus), water diabetes (diabetes insipidus), other hormone disorders (e.g., decreased pituitary hormone). If you have diabetes, this drug may affect your blood sugar. Check your blood sugar regularly as directed and share the results with your doctor. Tell your doctor right away if you have symptoms such as increased thirst/urination, shakiness, unusual sweating, dizziness, or hunger. Your doctor may need to adjust your diabetes medication, exercise program, or diet. Before having surgery, tell your doctor or dentist that you are taking this medication. Older adults may be more sensitive to the side effects of this drug, especially fast/pounding/irregular heartbeat. Children may be more sensitive to certain side effects of this drug, especially headache, vision changes, and hip/leg pain. High thyroid hormone levels may lead to decreased bone development/growth and reduced full adult height. Keep all lab/medical appointments so the doctor can monitor treatment. Current information shows that this drug may be used during pregnancy. Tell your doctor if you are pregnant or if you become pregnant because your dose may need to be adjusted. Small amounts of this drug pass into breast milk. While there have been no reports of harm to nursing infants, consult your doctor before breast-feeding.

DRUG INTERACTIONS: 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. Some products that may interact with this drug include: antidepressants (e.g., SSRIs such as sertraline, tricyclics such as amitriptyline), beta blockers (e.g., propranolol), corticosteroids (e.g., dexamethasone), cytokines (e.g., interferon alfa, interleukin-2), digoxin, epinephrine, ketamine, warfarin, drugs that can decrease thyroid hormone levels (e.g., amiodarone, medications containing iodide/iodine, lithium), drugs affecting liver enzymes that remove levothyroxine from your body (e.g., phenobarbital, rifamycins including rifampin, certain anti-seizure medicines including phenytoin). High doses of salicylates (e.g., high doses of aspirin) may affect thyroid hormone levels in the blood. However, low-dose aspirin should be continued if prescribed by your doctor for specific medical reasons such as heart attack or stroke prevention (usually at dosages of 81-325 milligrams per day). Ask your doctor or pharmacist for more details. 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 using those products safely.

OVERDOSE: 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 their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: fast/irregular heartbeat, chest pain, confusion, loss of consciousness.