About This Medicine

Make sure you know about each of the medicines you take. This includes why you take it, how to take it, what you can expect while you're taking it, and any warnings about the medicine.

The information provided here is general. So be sure to read the information that came with your medicine. If you have any questions or concerns, talk to your pharmacist or doctor.

What are some examples?

Here are some examples of levothyroxine. For each item in the list, the generic name is first, followed by any brand names.

• levothyroxine (T4) (Eltroxin, Synthroid)

This is not a complete list of medicines for low thyroid.

Why is levothyroxine used?

Levothyroxine is used to treat hypothyroidism. It's also used to treat an enlarged thyroid gland (goiter). You may use this medicine if your thyroid gland doesn't make enough thyroid hormone. Your body needs this hormone to work as it should.

How does it work?

Levothyroxine replaces a hormone that the thyroid gland usually makes.

What should you know about side effects?

All medicines can cause side effects. Many people don't have side effects. And minor side effects sometimes go away after a while.

But sometimes side effects can be a problem or can be serious.

If you're having problems with side effects, talk to your doctor. He or she may be able to lower your dose or change to a different medicine.

Always be sure you get specific information on the medicine you're taking. For a full list of side effects, check the information that came with the medicine you're using. If you have questions, talk to your pharmacist or doctor.

What are some cautions about levothyroxine?

Cautions for levothyroxine include the following:

• If your dose of medicine is too high, you may feel nervous, have irregular heartbeats, or have problems sleeping. You may also have tremors (shaking). And over time, you may develop osteoporosis. If you have heart disease, too much medicine can cause pain (angina) and irregular heartbeats.
• If your dose is too low, you may have symptoms of hypothyroidism. These include constipation, confusion, feeling sluggish or cold, and gaining weight.

General cautions for all medicines

Allergic reactions.

All medicines can cause a reaction. This can sometimes be an emergency. Before you take any new medicine, tell the doctor or pharmacist about any past allergic reactions you've had.

Drug interactions.

Sometimes one medicine may keep another medicine from working well. Or you may get a side effect you didn't expect. Medicines may also interact with certain foods or drinks, like grapefruit juice and alcohol. Some interactions can be dangerous.

Harm during pregnancy or breastfeeding.

If you are pregnant, trying to get pregnant, or breastfeeding, ask your doctor or pharmacist if all the medicines you take are safe.

Other health problems.

Before taking a medicine, be sure your doctor or pharmacist knows about all your health problems. The medicine for one health problem may affect another health problem.

Always tell your doctor or pharmacist about all the medicines you take. This includes prescription and over-the-counter medicines and natural health products. That information will help prevent serious problems.

Always be sure you get specific information on the medicine you're taking. For a full list of warnings, check the information that came with the medicine you're using. If you have questions, talk to your pharmacist or doctor.