Levothyroxine Tablets

Levothyroxine is a medication that treats hypothyroidism or low thyroid levels in your body. It works by replacing a thyroid hormone normally made by your body. Your thyroid hormone helps support your metabolism and energy levels.

What is this medication?

LEVOTHYROXINE (lee voe thye ROX een) treats low thyroid levels (hypothyroidism) in your body. It works by replacing a thyroid hormone normally made by the body. Thyroid hormones play an important role in your overall health. They help support metabolism and energy levels.

This medicine may be used for other purposes; ask your health care provider or pharmacist if you have questions.

COMMON BRAND NAME(S): Estre, Euthyrox, Levo-T, Levothroid, Levoxyl, Synthroid, Thyro-Tabs, Unithroid


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What should I tell my care team before I take this medication?

They need to know if you have any of these conditions:

  • Addison's disease or other adrenal gland problem
  • Angina
  • Bone problems
  • Dieting or on a weight loss program
  • Fertility problems
  • Heart disease
  • High blood sugar (diabetes)
  • Pituitary gland problem
  • Take medications that treat or prevent blood clots
  • An unusual or allergic reaction to levothyroxine, thyroid hormones, other medications, foods, dyes, or preservatives
  • Pregnant or trying to get pregnant
  • Breast-feeding

How should I use this medication?

Take this medication by mouth with plenty of water. It is best to take on an empty stomach, at least 30 minutes to one hour before breakfast. Avoid taking antacids containing aluminum or magnesium, simethicone, bile acid sequestrants, calcium carbonate, sodium polystyrene sulfonate, ferrous sulfate, sevelamer, lanthanum, or sucralfate within 4 hours of taking this medication. Follow the directions on the prescription label. Take at the same time each day. Do not take your medication more often than directed.

Contact your care team regarding the use of this medication in children. While this medication 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 to 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.

Overdosage: If you think you have taken too much of this medicine contact a poison control center or emergency room at once.

NOTE: This medicine is only for you. Do not share this medicine with others.


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 medication?

  • Amiodarone
  • Antacids
  • Calcium supplements
  • Carbamazepine
  • Certain medications for depression
  • Certain medications to treat cancer
  • Cholestyramine
  • Clofibrate
  • Colesevelam
  • Colestipol
  • Digoxin
  • Female hormones, like estrogens and birth control pills, patches, rings, or injections
  • Iron supplements
  • Ketamine
  • Lanthanum
  • Liquid nutrition products like Ensure
  • Lithium
  • Medications for colds and breathing difficulties
  • Medications for diabetes
  • Medications for hyperthyroidism
  • Medications or dietary supplements for weight loss
  • Methadone
  • Niacin
  • Orlistat
  • Oxandrolone
  • Phenobarbital or other barbiturates
  • Phenytoin
  • Rifampin
  • Sevelamer
  • Simethicone
  • Sodium polystyrene sulfonate
  • Soy isoflavones
  • Steroid medications like prednisone or cortisone
  • Sucralfate
  • Testosterone
  • Theophylline
  • Warfarin

This list may not describe all possible interactions. Give your health care provider a list of all the medicines, herbs, non-prescription drugs, or dietary supplements you use. Also tell them if you smoke, drink alcohol, or use illegal drugs. Some items may interact with your medicine.


What should I watch for while using this medication?

Be sure to take this medication 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 medication is taken with the right amount of water or other fluids.

Do not switch brands of this medication unless your care team 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 medication for an underactive thyroid, it may be several weeks before you notice an improvement. Check with your care team if your symptoms do not improve.

It may be necessary for you to take this medication for the rest of your life. Do not stop using this medication unless your care team advises you to.

This medication 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 care team that you are taking this medication.

What side effects may I notice from receiving this medication?

Side effects that you should report to your care team as soon as possible:

  • Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
  • Anxiety, nervousness
  • Excessive sweating or sensitivity to heat
  • Fever
  • Heart palpitations—rapid, pounding, or irregular heartbeat
  • Heart rhythm changes—fast or irregular heartbeat, dizziness, feeling faint or lightheaded, chest pain, trouble breathing
  • Irregular menstrual cycles or spotting
  • Severe diarrhea
  • Tremors or shaking
  • Trouble sleeping

Side effects that usually do not require medical attention (report to your care team if they continue or are bothersome):

  • Changes in appetite
  • Hair loss
  • Headache
  • Nausea
  • Vomiting

This list may not describe all possible side effects. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Where should I keep my medication?

Keep out of the reach of children and pets.

Store at room temperature between 15 and 30 degrees C (59 and 86 degrees F). Protect from light and moisture. Keep container tightly closed. Throw away any unused medication after the expiration date.

NOTE: This sheet is a summary. It may not cover all possible information. If you have questions about this medicine, talk to your doctor, pharmacist, or health care provider.

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Note: Introduction and Additional Common Questions written and medically approved by Cleveland Clinic professionals.

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