levothyroxine (generic name)

This medicine can improve symptoms of thyroid deficiency such as slow speech, lack of energy, weight gain, hair loss, dry skin, and feeling cold
(lee voe thye ROX een)
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What is this medicine?

LEVOTHYROXINE (lee voe thye ROX een) is a thyroid hormone. This medicine can improve symptoms of thyroid deficiency such as slow speech, lack of energy, weight gain, hair loss, dry skin, and feeling cold. It also helps to treat goiter (an enlarged thyroid gland). It is also used to treat some kinds of thyroid cancer along with surgery and other medicines.

What should I tell my health care provider before I take this medicine?

They need to know if you have any of these conditions:
  • angina
  • blood clotting problems
  • diabetes
  • dieting or on a weight loss program
  • fertility problems
  • heart disease
  • high levels of thyroid hormone
  • pituitary gland problem
  • previous heart attack
  • an unusual or allergic reaction to levothyroxine, thyroid hormones, other medicines, foods, dyes, or preservatives
  • pregnant or trying to get pregnant
  • breast-feeding

How should I use this medicine?

Take this medicine by mouth with plenty of water. It is best to take on an empty stomach, at least 30 minutes before or 2 hours after food. Follow the directions on the prescription label. Take at the same time each day. Do not take your medicine more often than directed.

Contact your pediatrician regarding the use of this medicine in children. While this drug may be prescribed for children and infants as young as a few days of age for selected conditions, precautions do apply. For infants, you may crush the tablet and place in a small amount of (5-10 ml or 1 to 2 teaspoonfuls) of water, breast milk, or non-soy based infant formula. Do not mix with soy-based infant formula. Give as directed.

What if I miss a dose?

If you miss a dose, take it as soon as you can. If it is almost time for your next dose, take only that dose. Do not take double or extra doses.

What may interact with this medicine?

  • amiodarone
  • antacids
  • anti-thyroid medicines
  • calcium supplements
  • carbamazepine
  • cholestyramine
  • colestipol
  • digoxin
  • female hormones, including contraceptive or birth control pills
  • iron supplements
  • ketamine
  • liquid nutrition products like Ensure
  • medicines for colds and breathing difficulties
  • medicines for diabetes
  • medicines for mental depression
  • medicines or herbals used to decrease weight or appetite
  • phenobarbital or other barbiturate medications
  • phenytoin
  • prednisone or other corticosteroids
  • rifabutin
  • rifampin
  • soy isoflavones
  • sucralfate
  • theophylline
  • warfarin

What should I watch for while using this medicine?

Be sure to take this medicine with plenty of fluids. Some tablets may cause choking, gagging, or difficulty swallowing from the tablet getting stuck in your throat. Most of these problems disappear if the medicine is taken with the right amount of water or other fluids.

Do not switch brands of this medicine unless your health care professional agrees with the change. Ask questions if you are uncertain.

You will need regular exams and occasional blood tests to check the response to treatment. If you are receiving this medicine for an underactive thyroid, it may be several weeks before you notice an improvement. Check with your doctor or health care professional if your symptoms do not improve.

It may be necessary for you to take this medicine for the rest of your life. Do not stop using this medicine unless your doctor or health care professional advises you to.

This medicine can affect blood sugar levels. If you have diabetes, check your blood sugar as directed.

You may lose some of your hair when you first start treatment. With time, this usually corrects itself.

If you are going to have surgery, tell your doctor or health care professional that you are taking this medicine.

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Last Updated: March 26, 2010
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