Synthroid (Levothyroxine)







What is Synthroid?

Synthroid (levothyroxine) is a replacement for a hormone that is normally produced by your thyroid gland to regulate the body's energy and metabolism. Synthroid is given when the thyroid does not produce enough of this hormone on its own.

Synthroid treats hypothyroidism (low thyroid hormone). Levothyroxine is also used to treat or prevent goiter (enlarged thyroid gland), which can be caused by hormone imbalances, radiation treatment, surgery, or cancer.

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

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

Important information about Synthroid

Since thyroid hormone occurs naturally in the body, almost anyone can take Synthroid. You should not use Synthroid if you have had a heart attack, a thyroid disorder called thyrotoxicosis, or an adrenal gland problem that is not controlled by treatment.

Before you take Synthroid, tell your doctor if you have a serious thyroid disorder (thyrotoxicosis), heart disease, coronary artery disease, diabetes, anemia, problems with your pituitary or adrenal glands, a history of blood clots, if you have recently had a heart attack, or if you are having any symptoms of a heart attack (chest pain or heavy feeling, pain spreading to the arm or shoulder, nausea, sweating, general ill feeling).

If you use insulin or take diabetes medicine by mouth, ask your doctor if your dose needs to be changed when you start using Synthroid.

Different brands of levothyroxine may not work the same. If you get a prescription refill and your new pills look different, talk with your pharmacist or doctor.

It may take several weeks before your body starts to respond to Synthroid. Do not stop taking the medicine suddenly. Even if you feel well, you may still need to take this medicine every day for the rest of your life to replace the thyroid hormone your body cannot produce.

Tell your doctor about all medications you use. This includes prescription, over-the-counter, vitamin, and herbal products. Do not start a new medication without telling your doctor. Keep a list of all your medicines and show it to any healthcare provider who treats you.

Before taking Synthroid

Since thyroid hormone occurs naturally in the body, almost anyone can take Synthroid. However, you may not be able to take this medication if you have certain medical conditions.

To make sure you can safely take Synthroid, tell your doctor if you have:

  • a thyroid disorder called thyrotoxicosis;

  • heart disease, coronary artery disease, or a history of blood clots;

  • diabetes;

  • anemia (lack of red blood cells);

  • problems with your pituitary or adrenal glands;

  • an untreated or uncontrolled adrenal gland disorder; or

  • if you have recently had a heart attack, or are having any symptoms of a heart attack (chest pain or heavy feeling, pain spreading to the arm or shoulder, nausea, sweating, general ill feeling).

If you use insulin or take diabetes medicine by mouth, ask your doctor if your dose needs to be changed when you start using Synthroid.

FDA pregnancy category A. Synthroid is not expected to harm an unborn baby. If you become pregnant while taking Synthroid, do not stop taking the medicine without your doctor's advice. Having low thyroid hormone levels during pregnancy could harm both mother and baby. Your dose needs may be different during pregnancy. Levothyroxine can pass into breast milk, but it is not expected to be harmful to a nursing baby. Do not use Synthroid without telling your doctor if you are breast-feeding a baby. Your dose needs may be different while you are nursing.

In most cases, you will need to take Synthroid for the rest of your life. Taking Synthroid over long periods of time may cause bone loss, which can lead to osteoporosis. Talk with your doctor about how this could affect you.

How should I take Synthroid?

Take Synthroid exactly as prescribed by your doctor. Do not take in larger or smaller amounts or for longer than recommended. Follow the directions on your prescription label.

Your doctor may occasionally change your dose to make sure you get the best results.

It is very important to take Levoxyl with a full glass (8 ounces) of water. The Levoxyl tablet can dissolve very quickly and swell in the throat, possibly causing choking or gagging. Take Synthroid on an empty stomach, 30 minutes before eating. Synthroid is usually taken in the morning. Follow your doctor's dosing instructions and try to take the medicine at the same time each day. It may take several weeks before your body starts to respond to this medication. Do not stop taking this medication suddenly. Even if you feel well, you may still need to take Synthroid every day for the rest of your life to replace the thyroid hormone your body cannot produce.

To be sure this medicine is helping your condition and is not causing harmful effects, your blood will need to be tested often. Your liver and kidney function may also need to be tested. Visit your doctor regularly.

Tell any doctor or dentist who treats you that you are using Synthroid.

Store Synthroid at room temperature away from moisture and heat.

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.




What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include chest pain, pounding heartbeats, tremors, shortness of breath, leg cramps, confusion, vomiting, diarrhea, or seizures.

What should I avoid while taking Synthroid?

Certain medicines can make Synthroid less effective if taken at the same time. If you use any of the following drugs, avoid taking them within 4 hours before or 4 hours after you take Synthroid:

  • calcium carbonate (Caltrate, Citracal, Oystercal, and others);

  • ferrous sulfate iron supplement;

  • sucralfate (Carafate);

  • sodium polystyrene sulfonate (Kayexalate, Kionex, and others);

  • antacids that contain aluminum (Amphojel, Gaviscon, Maalox, Mylanta, Riopan, Rulox, Tums, and others); and

  • cholesterol-lowering drugs cholestyramine (Questran) and colestipol (Colestid).

Do not change brands or change to a generic levothyroxine drug product without first asking your doctor. Different brands of levothyroxine may not work the same. If you get a prescription refill and your new pills look different, talk with your pharmacist or doctor.

Avoid the following food products, which can make your body absorb less levothyroxine: infant soy formula, cotton seed meal, walnuts, and high-fiber foods.

Synthroid side effects

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

Call your doctor at once if you have a serious side effect such as:

  • headache;

  • sleep problems (insomnia);

  • feeling nervous or irritable;

  • fever, hot flashes, sweating;

  • pounding heartbeats or fluttering in your chest;

  • changes in your menstrual periods; or

  • appetite changes, weight changes.

Less serious Synthroid side effects may include mild hair loss.

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.

What other drugs will affect Synthroid?

Tell your doctor if you have recently received radiation therapy with iodine (such as I-131).

Many other medicines can be affected by your thyroid hormone levels. Other medicine may also increase or decrease the effects of Synthroid, or may interact with Synthroid.

Tell your doctor about all medications you use. This includes prescription, over-the-counter, vitamin, and herbal products. Do not start a new medication without telling your doctor. Keep a list of all your medicines and show it to any healthcare provider who treats you.








Synthroid (Levothyroxine)
Synthroid (Levothyroxine)