Levothyroxine (Synthroid)

Levothyroxine (Synthroid)

Levothyroxine is a medicine used to treat people with hypothyroidism.

Hypothyroidism means a person’s thyroid gland doesn’t make enough thyroid hormone. People with this condition may no longer have a functioning thyroid, or hypothyroidism can be caused by a variety of other reasons that affect thyroid hormone production.

Levothyroxine is also used to prevent or treat a goiter (an enlarged thyroid gland) or with other therapies to treat thyroid cancer.

This drug is a hormone, which works by replacing thyroid hormone that your body normally produces.

The U.S. Food and Drug Administration (FDA) initially approved this medicine in 1969. It’s marketed under various brands.

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What is Levothyroxine (Synthroid) used for?

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What is the most important information I should know about Levothyroxine (Synthroid)?

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.

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 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:

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

  • 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.
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Side Effects

What are the side effects of Levothyroxine (Synthroid)?

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

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

Common side effects may include:

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.

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Pregnancy & Breastfeeding

Can I take Levothyroxine (Synthroid) if I’m pregnant or breastfeeding?

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.

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What drugs and food should I avoid while taking Levothyroxine (Synthroid)?

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.

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Dosage Guidelines & Tips

How to take Levothyroxine (Synthroid)?

Use Levothyroxine (Synthroid) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

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 is taken by mouth. Levothyroxine is given into a vein. oralinjection

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

Your dose needs may change if you switch to a different brand, strength, or form of this medicine. 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 each or in the blister pack until you are ready to take one. tablet capsule

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

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

Take levothyroxine on an empty stomach, at least 30 to 60 minutes before breakfast with a full glass of water. Take the medicine at the same time each day. oral

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

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

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

What should I do if I missed a dose of Levothyroxine (Synthroid)?

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

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

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Overdose Signs

What happens if I overdose on Levothyroxine (Synthroid)?

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

If you think you or someone else may have overdosed on: Levothyroxine (Synthroid),  call your doctor or the Poison Control center
(800) 222-1222
If someone collapses or isn't breathing after taking Levothyroxine (Synthroid), call 911
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What to Expect

Levothyroxine starts working right away, but it may take several weeks before you notice that your symptoms improve.

Usually, treatment with levothyroxine is lifelong. If you stop taking it, your symptoms will return.
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Additional Dosage Information

Your dosage will depend on your age, your medical condition, and other factors.

Your physician may need to adjust your dosage if you’re pregnant or if you have heart problems. They may also need to periodically change your dose on the basis of your blood tests.

Most of the time, side effects occur because you’re taking a larger dose than you need. If you experience side effects, your doctor can lower your dose.

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Secondary Uses

Levothyroxine is sometimes used as an “off-label” treatment for subclinical hypothyroidism — a mild, but very common, form of hypothyroidism.

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Medical Disclaimer

Drugs A-Z provides drug information from Everyday Health and our partners, as well as ratings from our members, all in one place. Cerner Multum™ provides the data within some of the Overview, Uses, Warnings, Side Effects, Pregnancy, Interactions, Dosage, Overdose, and Images sections. The information within all other sections is proprietary to Everyday Health.