Watch Out For Those Antacids: Medications that Interfere with Levothyroxine...

Some medications will be with someone the rest of their life. Levothyroxine is one of those for many people. 

"Levothyroxine, commonly known as Levothroid, Levoxyl, Synthroid, Tirosint and Unithroid, is a replacement for a hormone normally produced by your thyroid gland to regulate the body's energy and metabolism. This medication is given when the thyroid does not produce enough of this hormone on its own.

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

Whenever prescribed a new medication, take some time to see what other medications/herbs/lifestyle habits may interfere with the new medicine. 

The following comes from Mosby's 2012 Nursing Drug Reference

Medications that 
Decrease Levothyroxine Absorption 

Ferrous Sulfate (an iron supplement used to treat or prevent low blood levels of iron).  

Questran/Cholestyramine (used to lower cholesterol in the blood). 

Colestid/Colestipol (used to lower cholesterol in the blood). 

Medications that 

Decrease Levothyroxine Effectiveness 


It is recommended to avoid antacids containing magnesium, aluminum, calcium and iron. If you are using antacids, take them at least 4 hours from when you take your dose of Levothyroxine. 

Carafate/Sucralfate (used to treat and prevent ulcers in the intestines).



Aluminum, Magnesium, Calcium, Iron 

Drugs/Herbs that 
Decrease Thyroid Hormone Effect 


Whether those with hypothyroidism should avoid soy has long been a topic of debate. It is thought that soy interferes with the bodies ability to absorb Levothyroxine. However, the evidence is not strong enough to suggest people should avoid soy altogether. 

To be safe, you should not ingest anything containing soy within 4 hours of taking your medication. 


Is a vegetarian gelatin substitute produced from a variety of seaweed vegetation.

Bugleweed Carnitine 

Is a plant and people use the part that grows above the ground for medicine. 

**Used to help lower HIGH levels of Thyroid** 


Also known as Bladderwrack which is a type of seaweed. People use the whole plant to make medicine. 

Bladderwrack can potentially be contaminated with heavy metals due to pollution of the oceans and seas. Because of this, be careful when using these supplements.

A Few Notes About Taking Levothyroxine

- Take in A.M. on an empty stomach. 

(Though there are several people who have found taking Levothyroxine at night helpful, always discuss such a change with your healthcare professional). 

- Separate antacids, iron and calcium products by at least 4 hours. 

- Avoid OTC preparations containing iodine.

- Avoid iodine food, iodized salt, soybeans, tofu, turnips, high-iodine seafood.

- Caregivers should report excitability, irritability, anxiety (indicators of overdose). 

Does anyone have any other tips/tricks to share regarding taking Levothyroxine? Tell us about it in the comments. 

Sources Cited:

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