Can you take thyroid supplements with levothyroxine?

Taking any other medication or supplement with levothyroxine may cause you to need a higher or lower dose of levothyroxine. Even supplements like calcium or iron can affect absorption of levothyroxine.

According to the complete prescribing information for levothyroxine, many drugs can change the absorption, breakdown or response to levothyroxine. That could mean you get too much effect or too little.

The main problem with over-the-counter supplements is that they are not regulated. They may not contain what they say on the label, or the amount may be higher or lower than stated. According to a review of thyroid supplements in the journal Nutrients, 70% of supplements on the market don’t have the ingredients stated on the label or they have contaminants.

The most common thyroid supplements are:

• L-carnitine
• Myoinositol
• Melatonin
• Resveratrol
• Selenium

Although all of these may have some effect on thyroid hormone, none have been studied enough in people to know exactly how they affect levothyroxine in your body.

If you are taking levothyroxine, it is important to let your doctor know about any new drug or supplement you may take.