Synthroid (Levothyroxine) is a thyroid hormone used to treat hypothyroidism. It may also be used to treat other conditions as determined by your doctor.
Medication guide about Synthroid (Levothyroxine)
Brand name: Synthroid
Generic name: Levothyroxine
What is the most important information I should know about Synthroid?
There are many other medicines that can affect Synthroid. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor.
Different brands of Synthroid may not work the same. If you get a prescription refill and your new pills look different, talk with your pharmacist or doctor.
What is Synthroid?
Synthroid 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). Synthroid 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 other than those listed in this medication guide.
What should I discuss with my healthcare provider before taking Synthroid?
Since thyroid hormone occurs naturally in the body, almost anyone can take Synthroid. You should not use this medication if you have had a heart attack, a thyroid disorder called thyrotoxicosis, or an adrenal gland problem that is not controlled by treatment.
Before taking this medication, tell your doctor if you have heart disease, coronary artery disease, anemia (lack of red blood cells), diabetes, problems with your pituitary or adrenal glands, or a history of blood clots. You may not be able to take Synthroid, or you may need a dosage adjustment or special monitoring.
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.
Synthroid is in the FDA pregnancy category A. This means that it is safe to use while you are pregnant. It is also safe to use while you are breast-feeding a baby. This drug does pass into breast milk, but it is not expected to be harmful to a nursing infant.
Tell your doctor if you become pregnant during treatment. You may need to increase your dose during pregnancy or if you plan to breast-feed.
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 your doctor has prescribed it for you. Do not use more of the medication than recommended. Do not take Synthroid for longer than your doctor has prescribed.
Your doctor may occasionally change your dose to make sure you get the best results from this medication.
It is very important to take Synthroid with a full glass (8 ounces) of water. The Synthroid tablet can dissolve very quickly and swell in the throat, possibly causing choking or gagging.
Take this medicine 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 this medication 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 this medicine every day for the rest of your life to replace the thyroid hormone your body cannot produce.
To be sure this medication is helping your condition, your blood will need to be tested on a regular basis. Your kidney or liver function may also need to be tested. It is important that you not miss any scheduled visits to your doctor.
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. If it is almost time for your next dose, skip the missed dose and take the medicine at the next regularly scheduled time. Do not take extra medicine to make up the missed dose.
What happens if I overdose?
Seek emergency medical attention if you think you have used too much of this medicine.
Symptoms of a Synthroid overdose may include chest pain, pounding heartbeat, shortness of breath, tremor, shortness of breath, leg cramps, confusion, vomiting, diarrhea, or seizures.
What should I avoid while taking Synthroid?
Do not change brands or change to a generic Synthroid drug product without first asking your doctor. Different brands of Synthroid 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 Synthroid: infant soy formula, cotton seed meal, walnuts, and high-fiber foods.
What are the possible side effects of Synthroid?
Stop using Synthroid and get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have any of these serious side effects:
sleep problems (insomnia);
nervous or irritable feeling;
fever, hot flashes, sweating;
changes in your menstrual periods;
appetite changes, weight changes;
Other, less serious side effects may be more likely to occur. You may experience mild hair loss. Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.
What other drugs will affect Synthroid?
The following drugs may cause medical problems if you use them with Synthroid: lithium, amiodarone, or antidepressants. Tell your doctor if you have recently received radiation therapy with iodine (such as I-131).
There are many other drugs not listed that can affect Synthroid. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor.
Certain medicines can be continued, but they may make Synthroid less effective if taken at the same time. If you use any of the following drugs, use them at least 4 hours before or 4 hours after you take Synthroid:
calcium carbonate (Caltrate, Citracal, Oystercal, and others);
ferrous sulfate iron supplement;
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).