Generic name: levothyroxine (oral/injection) [ LEE-voe-thye-ROX-een ]
Brand names: Ermeza, Euthyrox, Levo-T, Levoxyl, Synthroid, ... show all 19 brands Thyquidity, Tirosint, Tirosint-Sol, Unithroid, Levothroid, Levotabs, Eltroxin, Levotec, Oroxine, Eutroxsig, L THYROXINE ROCHE, LEVOTHYROX, Evotrox, Thyroxine Sodium Pentahydrate
Dosage forms: intravenous powder for injection (100 mcg (0.1 mg), 200 mcg (0.2 mg), 500 mcg (0.5 mg)), ... show all 50 dosage forms intravenous solution (100 mcg (0.1 mg)/mL, 20 mcg (0.02 mg)/mL, 40 mcg (0.04 mg)/mL), oral capsule (100 mcg (0.1 mg), 112 mcg (0.112 mg), 125 mcg (0.125 mg), 13 mcg (0.013 mg), 137 mcg (0.137 mg), 150 mcg (0.15 mg), 175 mcg (0.175 mg), 200 mcg (0.2 mg), 25 mcg (0.025 mg), 37.5 mcg (0.0375 mg), 44 mcg (0.044 mg), 50 mcg (0.05 mg), 62.5 mcg (0.0625 mg), 75 mcg (0.075 mg), 88 mcg (0.088 mg)), oral solution (100 mcg (0.1 mg)/5 mL, 100 mcg (0.1 mg)/mL, 112 mcg (0.112 mg)/mL, 125 mcg (0.125 mg)/mL, 13 mcg (0.013 mg)/mL, 137 mcg (0.137 mg)/mL, 150 mcg (0.15 mg)/5 mL, 150 mcg (0.15 mg)/mL, 175 mcg (0.175 mg)/mL, 200 mcg (0.2 mg)/mL, 25 mcg (0.025 mg)/mL, 37.5 mcg (0.0375 mg)/mL, 44 mcg (0.044mg)/mL, 50 mcg (0.05 mg)/mL, 62.5 mcg (0.0625 mg)/mL, 75 mcg (0.075 mg)/mL, 88 mcg (0.088 mg)/mL), oral tablet (100 mcg (0.1 mg), 112 mcg (0.112 mg), 125 mcg (0.125 mg), 137 mcg (0.137 mg), 150 mcg (0.15 mg), 175 mcg (0.175 mg), 200 mcg (0.2 mg), 25 mcg (0.025 mg), 300 mcg (0.3 mg), 50 mcg (0.05 mg), 75 mcg (0.075 mg), 88 mcg (0.088 mg))
Drug class: Thyroid drugs

Medically reviewed by Drugs.com on Feb 6, 2024. Written by Cerner Multum.

What is levothyroxine?

Levothyroxine oral is used in adults and children to treat hypothyroidism (underactive thyroid).

Levothyroxine oral is also used in adults and children along with surgery and radioactive iodine therapy to treat a certain type of thyroid cancer.

Levothyroxine oral capsule can only be used in adults and children at least 6 years old.

Levothyroxine injection is used in adults to treat hypothyroid coma.

There are many brand forms of levothyroxine available. Not all brands are listed on this medication guide.

Levothyroxine may also be used for purposes not listed in this medication guide.

Levothyroxine side effects

Get emergency medical help if you have signs of an allergic reaction: hives, difficult breathing, swelling of your face, lips, tongue, or throat.

Levothyroxine may cause serious side effects. Call your doctor at once if you have:

• sudden pain or trouble moving your hip, wrist, or back;

• fast or irregular heartbeats;

• chest pain, pain spreading to your jaw or shoulder;

• wheezing;

• fever, swollen glands, itching, joint pain, or not feeling well;

• nausea, vomiting, diarrhea; or

• high blood sugar--increased thirst, increased urination, dry mouth, fruity breath odor.

Common side effects of levothyroxine may include:

• fever, hot flashes, increased sweating;

• tiredness;

• skin rash, hair loss;

• chest pain, fast or irregular heartbeats, shortness of breath;

• headache, leg cramps, muscle pain or weakness;

• tremors, feeling nervous or irritable, sleep problems (insomnia);

• increased or change in appetite;

• weight loss or weight gain;

• changes in your menstrual periods; or

• vomiting, diarrhea.

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.

Warnings

You may not be able to use levothyroxine if you have certain medical conditions. Tell your doctor if you have an untreated or uncontrolled adrenal gland disorder or any heart problems such as a recent heart attack.

Levothyroxine should not be used to treat obesity or weight problems.

Taking more than your recommended dose will not make levothyroxine more effective, and may cause serious side effects.

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.

You should not use levothyroxine if you are allergic to glycerin or edetate disodium, or if you have an untreated or uncontrolled adrenal gland disorder.

Tell your doctor if you have or have ever had:

• a thyroid nodule;

• thyroiditis (inflammation of thyroid gland);

• heart problems such as a heart attack, stroke;

• a blood clot or a blood clotting disorder;

• diabetes (your diabetes medicine may need to be adjusted);

• anemia (low red blood cells);

• weak bones (osteoporosis), or low bone mineral density;

• problems with your pituitary or adrenal gland;

• an allergy to any food or drugs;

• recently received radiation therapy with iodine (such as I-131); or

• kidney disease.

Tell your doctor if you are pregnant or plan to become pregnant. Having hypothyroidism during pregnancy may increase the risk of premature birth or other complications. The benefit of treating hypothyroidism may outweigh any risks to the baby. Your dose needs may be different during pregnancy.

Tell your doctor if you are breastfeeding. Your dose needs may be different while you are nursing.

You may be more likely to have a broken bone while using levothyroxine. Talk with your doctor about ways to keep your bones healthy.

How should I use levothyroxine?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

Levothyroxine oral is taken by mouth. Levothyroxine injection is injected into a vein by a healthcare provider.

Take levothyroxine oral on an empty stomach, at least 15 to 60 minutes before breakfast with a full glass of water. Take the medicine at the same time each day.

Swallow the capsule whole and do not crush, chew, break, or open it.

If you cannot swallow a tablet whole, crush the tablet, and mix with 1 or 2 teaspoons of water; give the mixture right away. Do not save it for later use.

Tell your doctor if your child cannot swallow a capsule whole.

Measure liquid medicine with the supplied measuring device (not a kitchen spoon).

Doses are based on weight in children and teenagers. Your child's dose may change if the child gains or loses weight.

Your dose needs may change if you switch to a different brand, strength, or form of levothyroxine. Avoid medication errors by using only the medicine your doctor prescribes.

Keep using this medicine even if you feel well. You may not fully benefit from this medicine for several weeks.

You will need frequent medical tests, and your next dose may be delayed based on the results.

This medicine can affect the results of certain medical tests. Tell any doctor who treats you that you are using levothyroxine.

Tell your doctor if you have a planned surgery or dental procedure.

Taking more than your recommended dose will not make this medicine more effective, and may cause serious side effects.

Keep the tablet or capsule in the blister pack until you are ready to take the medication.

Store Ermeza and Thyquidity in the original bottle. Use Ermeza within 90 days and Thyquidity within 8 weeks of opening the bottle.

Use Tirosint-Sol within 3 months after opening the pouch.

Store at room temperature away from moisture, heat, and light.

What happens if I miss a dose?

In a medical setting you are not likely to miss a dose of levothyroxine injection.

Take the levothyroxine oral as soon as you remember, and then go back to your regular schedule. Do not use two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. An overdose can be fatal.

Overdose symptoms may include headache, leg cramps, tremors, feeling nervous or irritable, chest pain, shortness of breath, fast or pounding heartbeats, stroke, and coma.

What should I avoid while using levothyroxine?

Avoid the following food products within 1 hour of taking levothyroxine oral or the medication will not be as effective: grapefruit juice, infant soy formula, soybean flour, cotton seed meal, walnuts, and high-fiber foods.

What other drugs will affect levothyroxine?

Sometimes it is not safe to use certain medicines at the same time. Some drugs can affect your thyroid hormone levels and also make levothyroxine less effective.

If you use any of the following drugs, avoid taking them within 4 hours before or 4 hours after you use levothyroxine:

• calcium carbonate (Alka-Mints, Caltrate, Os-Cal, Oyster Shell Calcium, Rolaids Soft Chew, Tums, and others);

• sevelamer, lanthanum;

• cholestyramine, colesevelam, colestipol;

• iron supplements;

• sucralfate;

• sodium polystyrene sulfonate (Kalexate, Kayexalate, Kionex);

• stomach acid reducers--esomeprazole, lansoprazole, omeprazole, rabeprazole, Nexium, Prilosec, Prevacid, Protonix, Zegerid, and others; or

• antacids that contain aluminum or magnesium--Gaviscon, Maalox, Milk of Magnesia, Mintox, Mylanta, Pepcid Complete, and others.

Tell your doctor about all your other medicines, especially:

• orlistat;

• phenobarbital, rifampin;

• ketamine, steroid medicines;

• antidepressants such as amitriptyline or maprotiline;

• heart or blood pressure medication;

• diabetes medications;

• cancer medicine such as imatinib; or

• a blood thinner--warfarin, Coumadin, Jantoven.

This list is not complete and many other drugs may affect levothyroxine. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

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Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Medical Disclaimer

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