Generic Name: Levothyroxine Tablets (lee voe thye ROKS een)
Brand Name: Euthyrox, Levoxyl, Synthroid
Medically reviewed by Drugs.com. Last updated on Feb 18, 2019.
- Do not use Synthroid (levothyroxine tablets) to treat obesity or for weight loss. Very bad and sometimes deadly side effects may happen with Synthroid (levothyroxine tablets) if it is taken in large doses or with other drugs for weight loss. Talk with the doctor.
Uses of Synthroid:
- It is used to add thyroid hormone to the body.
- It is used to manage thyroid cancer.
- It may be given to you for other reasons. Talk with the doctor.
What do I need to tell my doctor BEFORE I take Synthroid?
- If you have an allergy to levothyroxine or any other part of Synthroid (levothyroxine tablets).
- If you are allergic to any drugs like this one, any other drugs, foods, or other substances. Tell your doctor about the allergy and what signs you had, like rash; hives; itching; shortness of breath; wheezing; cough; swelling of face, lips, tongue, or throat; or any other signs.
- If you have any of these health problems: Overactive thyroid gland or weak adrenal gland.
- If you have trouble swallowing.
This is not a list of all drugs or health problems that interact with Synthroid (levothyroxine tablets).
Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take Synthroid (levothyroxine tablets) with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor.
What are some things I need to know or do while I take Synthroid?
For all patients taking Synthroid (levothyroxine tablets):
- Tell all of your health care providers that you take Synthroid (levothyroxine tablets). This includes your doctors, nurses, pharmacists, and dentists.
- Do not run out of Synthroid (levothyroxine tablets).
- It may take several weeks to see the full effects.
- If you have high blood sugar (diabetes), Synthroid (levothyroxine tablets) may sometimes raise blood sugar. Talk with your doctor about how to keep your blood sugar under control.
- Check your blood sugar as you have been told by your doctor.
- Have blood work checked as you have been told by the doctor. Talk with the doctor.
- This medicine may cause weak bones (osteoporosis) with doses that are too high. The risk may be higher in women who have been through menopause. Talk with your doctor to see if you have a higher risk of weak bones or if you have any questions.
- This medicine may affect fertility. Fertility problems may lead to not being able to get pregnant or father a child. Talk with the doctor.
- If you are 65 or older, use Synthroid (levothyroxine tablets) with care. You could have more side effects.
- Tell your doctor if you are pregnant, plan on getting pregnant, or are breast-feeding. You will need to talk about the benefits and risks to you and the baby.
- If giving Synthroid (levothyroxine tablets) to your child and your child's weight changes, talk with the doctor. The dose of Synthroid (levothyroxine tablets) may need to be changed.
- This medicine may affect growth in children and teens in some cases. They may need regular growth checks. Talk with the doctor.
How is this medicine (Synthroid) best taken?
Use Synthroid (levothyroxine tablets) as ordered by your doctor. Read all information given to you. Follow all instructions closely.
- Take on an empty stomach at least 30 to 60 minutes before breakfast.
- Some products may cause choking, gagging, or trouble swallowing. These products must be taken with a full glass of water. Ask your pharmacist if you need to take your product with a full glass of water.
- You may crush tablet and mix with 1 or 2 teaspoons (5 or 10 mL) of water.
- Do not take iron products, antacids that have aluminum or magnesium, or calcium carbonate, within 4 hours before or 4 hours after taking Synthroid (levothyroxine tablets).
- If you take colesevelam, colestipol, cholestyramine, kayexalate, or sevelamer, take it at least 4 hours before or 4 hours after taking this drug.
- Some other drugs may need to be taken at some other time than Synthroid (levothyroxine tablets). If you take other drugs, check with your doctor or pharmacist to see if you need to take them at some other time than Synthroid (levothyroxine tablets).
- Some foods like soybean flour (infant formula) may change how Synthroid (levothyroxine tablets) works in your body. Talk with your doctor.
- If you drink grapefruit juice or eat grapefruit often, talk with your doctor.
- There is more than 1 brand of Synthroid (levothyroxine tablets). One brand cannot safely be used for the other. The doctor will tell you about any needed change.
- Keep taking Synthroid (levothyroxine tablets) as you have been told by your doctor or other health care provider, even if you feel well.
What do I do if I miss a dose?
- Take a missed dose as soon as you think about it.
- If it is close to the time for your next dose, skip the missed dose and go back to your normal time.
- Do not take 2 doses at the same time or extra doses.
What are some side effects that I need to call my doctor about right away?
WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:
- Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
- Signs of high blood pressure like very bad headache or dizziness, passing out, or change in eyesight.
- Chest pain or pressure.
- Fast or abnormal heartbeat.
- Shortness of breath, a big weight gain, or swelling in the arms or legs.
- Feeling tired or weak.
- Feeling more or less hungry.
- A change in weight without trying.
- Stomach cramps.
- Throwing up.
- Feeling irritable.
- Feeling nervous and excitable.
- Emotional ups and downs.
- Trouble sleeping.
- Bothered by heat.
- Sweating a lot.
- Muscle cramps.
- Muscle weakness.
- Bone pain.
- Period (menstrual) changes.
What are some other side effects of Synthroid?
All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:
- Hair loss may happen in some people in the first few months of using Synthroid (levothyroxine tablets). This most often goes back to normal.
These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.
You may report side effects to the FDA at 1-800-FDA-1088. You may also report side effects at http://www.fda.gov/medwatch.
If OVERDOSE is suspected:
If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.
How do I store and/or throw out Synthroid?
- Store at room temperature.
- Protect from heat and light.
- Store in a dry place. Do not store in a bathroom.
- Some brands of Synthroid (levothyroxine tablets) come in a blister pack. If Synthroid (levothyroxine tablets) comes in a blister pack, do not take it out of the blister pack until you are ready to take it. Do not store the removed drug for future use.
- Keep all drugs in a safe place. Keep all drugs out of the reach of children and pets.
- Throw away unused or expired drugs. Do not flush down a toilet or pour down a drain unless you are told to do so. Check with your pharmacist if you have questions about the best way to throw out drugs. There may be drug take-back programs in your area.
Consumer information use
- If your symptoms or health problems do not get better or if they become worse, call your doctor.
- Do not share your drugs with others and do not take anyone else's drugs.
- Keep a list of all your drugs (prescription, natural products, vitamins, OTC) with you. Give this list to your doctor.
- Talk with the doctor before starting any new drug, including prescription or OTC, natural products, or vitamins.
- Some drugs may have another patient information leaflet. Check with your pharmacist. If you have any questions about Synthroid (levothyroxine tablets), please talk with your doctor, nurse, pharmacist, or other health care provider.
- If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
More about Synthroid (levothyroxine)
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- During Pregnancy or Breastfeeding
- Dosage Information
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- Drug class: thyroid drugs