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Levothyroxine (a thyroid hormone) should not be used alone or along with other treatments to treat obesity or cause weight loss.
Levothyroxine may cause serious or life-threatening problems when given in large doses, especially when taken with amphetamines such as amphetamine (Adzenys, Dyanavel XR, Evekeo), dextroamphetamine (Dexedrine), and methamphetamine (Desoxyn). Tell your doctor if you have any of the following symptoms while you are taking levothyroxine: chest pain, rapid or irregular heartbeat or pulse, uncontrollable shaking of a part of the body, nervousness, anxiety, irritability, difficulty falling asleep or staying asleep, shortness of breath, or excessive sweating.
Talk to your doctor about the potential risks associated with this medication.
WHY is this medicine prescribed?
Levothyroxine is used to treat hypothyroidism (condition where the thyroid gland does not produce enough thyroid hormone). It is also used with surgery and radioactive iodine therapy to treat thyroid cancer. Levothyroxine is in a class of medications called hormones. It works by replacing thyroid hormone that is normally produced by the body.
Without thyroid hormone, your body cannot function properly, which may result in poor growth, slow speech, lack of energy, excessive tiredness, constipation, weight gain, hair loss, dry, thick skin, increased sensitivity to cold, joint and muscle pain, heavy or irregular menstrual periods, and depression. When taken correctly, levothyroxine reverses these symptoms.
HOW should this medicine be used?
Levothyroxine comes as a tablet and a capsule to take by mouth. It usually is taken once a day on an empty stomach, 30 minutes to 1 hour before breakfast. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take levothyroxine exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
Swallow capsules whole; do not chew or crush them. Do not remove the capsule from the package until you are ready to take it.
Take the tablets with a full glass of water as they may get stuck in your throat or cause choking or gagging.
If you are giving levothyroxine to an infant, child, or adult who cannot swallow the tablet, crush and mix it in 1 to 2 teaspoons (5 to 10 mL) of water. Only mix the crushed tablets with water; do not mix it with food or soybean infant formula. Give this mixture by spoon or dropper right away. Do not store it for later use.
Your doctor will probably start you on a low dose of levothyroxine and gradually increase your dose.
Levothyroxine controls hypothyroidism but does not cure it. It may take several weeks before you notice a change in your symptoms. Continue to take levothyroxine even if you feel well. Do not stop taking levothyroxine without talking to your doctor.
Are there OTHER USES for this medication?
This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.
What SPECIAL PRECAUTIONS should I follow?
Before taking levothyroxine,
What SPECIAL DIETARY instructions should I follow?
Some foods and beverages, particularly those that contain soybeans, walnuts, and dietary fiber, may affect how levothyroxine works for you. Talk to your doctor before eating or drinking these foods.
Talk to your doctor about eating grapefruit and drinking grapefruit juice while taking this medication.
What should I do IF I FORGET to take a dose?
Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.
What SIDE EFFECTS can this medicine cause?
Levothyroxine may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
Some side effects can be serious. If you experience either of the following symptoms or those listed in the IMPORTANT WARNING section, call your doctor immediately or get emergency medical treatment:
If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).
What should I do in case of OVERDOSE?
In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at http://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.
Symptoms of overdose may include the following:
What should I know about STORAGE and DISPOSAL of this medication?
Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).
Keep all medication out of sight and reach of children as many containers are not child-resistant. Always lock safety caps. Place the medication in a safe location - one that is up and away and out of their sight and reach. http://www.upandaway.org
Dispose of unneeded medications in a way so that pets, children, and other people cannot take them. Do not flush this medication down the toilet. Use a medicine take-back program. Talk to your pharmacist about take-back programs in your community. Visit the FDA's Safe Disposal of Medicines website http://goo.gl/c4Rm4p for more information.
What OTHER INFORMATION should I know?
Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your response to levothyroxine.
Learn the brand name and generic name of your medication. Do not switch brands without talking to your doctor or pharmacist, as each brand of levothyroxine contains a slightly different amount of medication.
Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.
Keep a written list of all of the prescription and nonprescription (over-the-counter) medicines, vitamins, minerals, and dietary supplements you are taking. Bring this list with you each time you visit a doctor or if you are admitted to the hospital. You should carry the list with you in case of emergencies.
¶ This branded product is no longer on the market. Generic alternatives may be available.
This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.
The American Society of Health-System Pharmacists, Inc. represents that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists, Inc. makes no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information is not a substitute for medical care.
AHFS® Patient Medication Information™ Copyright, 2025. The American Society of Health-System Pharmacists®, 4500 East-West Highway, Suite 900, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.
Selected Revisions: February 15, 2019.