Is There Concern With Taking Magnesium With Levothyroxine?

Levothyroxine is not not as effective if you are taking magnesium at the same time.
Image Credit: Aleksandr_Gromov/iStock/GettyImages

When your thyroid doesn't produce enough thyroid hormone, you develop a condition known as hypothyroidism, and your doctor might prescribe levothyroxine for this condition. If you take both magnesium and levothyroxine, your body could experience an interaction with negative side effects.



Levothyroxine offsets the lack of thyroid hormone so your body continues to function properly when you are diagnosed with hypothyroidism. But the drug may not be as effective if you take magnesium.

Read more: How to Determine if a Vitamin or Supplement Is Actually Right for You

Video of the Day

Magnesium and Synthroid Interaction

According to the Mayo Clinic, magnesium hydroxide can interact with synthroid, also known as levothyroxine. This could cause an increase in adverse side effects, such as the levothyroxine not working properly. How does this occur?


The thyroid drug has a synthetic salt known as T4, similar to the substance the thyroid gland produces, according to the U.S. National Library of Medicine. When you take the drug and magnesium hydroxide during the same period, the magnesium can attach itself to T4. As a result, your body takes longer to absorb T4, or you might not be able to assimilate T4 at all. When that happens, you render the medication levothyroxine useless — wasting your time, money and above all, an ability to help your health.


When receiving a prescription for levothyroxine, the Mayo Clinic says you should let your doctor know you are taking a magnesium supplement. This doesn't mean your health care professional will have you stop taking it. He or she might switch the dosage or frequency of either the supplement and/or medication. Your doctor might also recommend a different magnesium supplement to ensure levothyroxine works properly.

Read more: 6 Symptoms of Vitamin B6 Toxicity to Alert Your Doctor


Potential Magnesium Replacements

If you feel trepidations about a magnesium and thyroid nodules medication interaction, you could seek potential replacements with your doctor's permission. According to the U.S. Department of Health & Human Services, magnesium forms that dissolve well in liquid are better for the gut. These include the supplements of magnesium aspartate, citrate, lactate and chloride.


You can also discuss with your doctor the possibility of adjusting your diet to raise your magnesium level. Potential magnesium food sources per serving, according to a September 2017 study from Scientifica, include the following:


  • Salmon (3 ounces)
  • Apple (1)
  • Boiled spinach (1/2 cup)
  • Avocado (1 cup, cubed)
  • Broccoli (1/2 cup, cooked)
  • Brown rice (1/2 cup)
  • Kidney beans (1/2 cup)
  • Hemp seeds (100 gm)
  • Pumpkin seeds (100 gm)
  • Whole wheat bread (2 slices)


You might not need a magnesium supplement at all. The U.S. Department of Health & Human Services says that symptomatic magnesium deficiency due to low diet intake in healthy people is uncommon because the kidneys limit the amount lost in urine excretion. You should speak with your health care professional if the removal of a magnesium supplement is indeed a possibility for your health.

If you do decide to stop supplementing your diet with magnesium because you take levothyroxine, be sure to watch out for symptoms of a magnesium deficiency. The U.S. Department of Health & Human Sciences says these include loss of appetite, nausea, vomiting, weakness and fatigue. You should speak with your doctor immediately if you experience any of these.

Read more: Could You Be Micronutrient Deficient and Not Know It?



references & resources

Report an Issue

screenshot of the current page

Screenshot loading...