This article describes possible interactions with levothyroxine oral tablet. Interactions can cause a drug to have a different effect on the body than expected. Interactions can occur due to medications, alcohol, or certain health conditions.
Levothyroxine comes as oral tablets that you’ll swallow. It’s also available as a solution for injection by a healthcare professional.
Boxed warning: Not for weight loss or treatment of obesity
Levothyroxine has a boxed warning stating the drug should not be used for weight loss or to treat obesity. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). See the end of this article for more information about this warning.
Other drugs and levothyroxine
The drugs in the list below may interact with levothyroxine oral tablet. This article does not include all drugs that may interact with levothyroxine.
Drug classes or drugs that may interact with levothyroxine oral tablet include:
- antacids:
- drug examples: calcium carbonate (Tums), aluminum hydroxide/magnesium hydroxide (Maalox)
- what might happen: can make levothyroxine less effective than usual
- bile acid sequestrants:
- drug examples: colestipol (Colestid), cholestyramine (Locholest, Prevalite)
- what might happen: can make levothyroxine less effective than usual
- certain seizure drugs:
- drug examples: carbamazepine (Tegretol, others), phenytoin (Dilantin)
- what might happen: can make levothyroxine less effective than usual
- beta-blockers, which may be used to treat high blood pressure:
- drug examples: metoprolol (Lopressor, Toprol XL), propranolol (Inderal LA)
- what might happen: can make the beta-blocker less effective than usual
- corticosteroids:
- drug examples: dexamethasone (Hemady), prednisone (Rayos)
- what might happen: can make levothyroxine less effective than usual and may raise the risk of side effects of levothyroxine
- phosphate binders:
- drug examples: lanthanum (Fosrenol), sevelamer (Renvela)
- what might happen: can make levothyroxine less effective than usual
- proton pump inhibitors (PPIs):
- drug examples: esomeprazole (Nexium), omeprazole (Prilosec)
- what might happen: can make levothyroxine less effective than usual
- amiodarone (Pacerone):
- what might happen: can make levothyroxine less effective than usual
- sucralfate (Carafate):
- what might happen: can make levothyroxine less effective than usual
- warfarin (Jantoven):
- what might happen: can increase the risk of side effects of warfarin
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Other interactions and levothyroxine
Interactions can occur with supplements, foods, vaccines, and some lab tests. Below you can learn whether levothyroxine oral tablet has these interactions.
The information below does not include all other possible interactions possible with levothyroxine.
Levothyroxine and supplements
Before taking levothyroxine oral tablet, tell your doctor and pharmacist about any herbs you take, as well as vitamins and supplements. Doing so may help you avoid interactions.
If you have questions about interactions that may affect you, talk with your doctor or pharmacist.
Levothyroxine interactions with herbs
Levothyroxine oral tablet is not known to interact with any herbs. But this does not mean interactions with herbs cannot happen or will not be identified later.
Because of this, ask your doctor or pharmacist before taking any of these products while using levothyroxine oral tablet.
Levothyroxine interactions with vitamins and minerals
Certain vitamins and minerals can interact with levothyroxine. These include:
Because of this, ask your doctor or pharmacist before taking any of these products while taking levothyroxine oral tablet. To help avoid this interaction, you should take the supplements listed at least 4 hours before or after taking levothyroxine.
Levothyroxine and food interactions
You should take levothyroxine with plain water on an empty stomach. It’s important that you do not eat food for at least 1 hour before taking levothyroxine oral tablet. If you take levothyroxine with food, an interaction could occur that lowers the level of the drug in your body. This may make levothyroxine less effective for your condition.
You should also avoid certain foods for at least 1 hour after you take a dose of levothyroxine. These include:
Because of this, talk with your doctor or pharmacist about what foods you should avoid while taking levothyroxine oral tablet.
Levothyroxine and vaccines
Levothyroxine oral tablet is not known to interact with any vaccines. But this does not mean interactions with vaccines cannot happen or will not be identified later.
Because of this, talk with your doctor or pharmacist before receiving any vaccines while taking levothyroxine oral tablet.
Levothyroxine and lab tests
Levothyroxine is not known to interact with lab tests. But this doesn’t mean interactions with lab tests cannot happen or will not be identified later.
Because of this, talk with your doctor or pharmacist before having any tests while taking levothyroxine oral tablet.
Levothyroxine and cannabis or CBD
Studies of cannabis (commonly called marijuana) and cannabis products have been shown to interact with levothyroxine. Cannabidiol (CBD) is an example of a cannabis product.
Taking levothyroxine and cannabis may lead to a lower or higher level of levothyroxine in your body. This could make levothyroxine less effective if it lowers levels of the drug. Or, it could raise your risk for side effects if it increases levels of levothyroxine in your system.
Before you take levothyroxine, tell your doctor and pharmacist if you use cannabis. Doing so may help prevent possible interactions.
Note: Cannabis is illegal at a federal level but is legal in many states to varying degrees.
Alcohol and levothyroxine
Levothyroxine oral tablet is not known to interact with alcohol.
If you drink alcohol, talk with your doctor about whether it’s safe to consume it while using levothyroxine oral tablet.
When to avoid levothyroxine
Certain health conditions or other factors could increase some risks with levothyroxine oral tablet. Because of this, doctors may not prescribe levothyroxine in these cases. These health conditions or other factors are called contraindications.
Here’s a list of contraindications for levothyroxine oral tablet:
- Adrenal insufficiency. If you have adrenal insufficiency that’s untreated, taking levothyroxine oral tablet may worsen your symptoms. (With adrenal insufficiency, your adrenal glands don’t produce as much hormone as usual.)
- Past allergic reaction to levothyroxine. If you’ve ever had an allergic reaction to levothyroxine oral tablet, taking it again may cause another allergic reaction.
Before you start taking Levothyroxine, tell your doctor if anything listed above relates to you. They can recommend whether you should take levothyroxine.
Health factors and levothyroxine
Certain medical conditions or other health factors may increase the risk of interactions with levothyroxine oral tablet. Keep in mind that interactions could lead to side effects or affect how well the drug works. Before taking levothyroxine, tell your doctor about your health history. They’ll determine whether levothyroxine is right for you.
These health conditions or other factors might interact with levothyroxine oral tablet:
Preventing levothyroxine interactions
You may be able to help avoid certain interactions with levothyroxine oral tablet. Before taking this drug, you may want to discuss possible interactions with your doctor and pharmacist.
Things to consider include:
- Whether you drink alcohol or use cannabis.
- Other medications and herbs you take, as well as vitamins and supplements. Your doctor or pharmacist can help you fill out a medication list.
- What to do if you’re prescribed a new drug while using levothyroxine oral tablet.
Taking levothyroxine exactly as prescribed can also help prevent interactions.
What to ask your doctor
If you have questions about levothyroxine and possible interactions, talk with your doctor.
Questions you may want to ask your doctor include:
- How long after taking levothyroxine can I take other medications?
- Do I need to take my medications at different times throughout the day to avoid interactions?
- Could I still take levothyroxine even if it interacts with a health condition I have?
- Does my levothyroxine dosage affect my risk for interactions?
Boxed warning for levothyroxine
Levothyroxine has a boxed warning stating the drug should not be used for weight loss or to treat obesity. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).
Levothyroxine will not be effective for weight loss in people without a thyroid condition. Further, using levothyroxine for this purpose can result in serious or even life threatening side effects.
To learn more, talk with your doctor.
Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.
