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Eltroxin and Interaction With Calcium

By Shelley Moore

Eltroxin is a brand name for the medication levothyroxine, a thyroid hormone. Your doctor may prescribe Eltroxin if your thyroid gland doesn't make enough thyroid hormone, a disorder known as hypothyroidism. Eltroxin also can treat an enlarged thyroid gland, known as a goiter. Eltroxin has a complicated interaction with calcium supplements, but you can work around this interaction.


Hypothyroidism is a common disorder, affecting over 13 million people in the United States as of 2004, according to an article published in a 2004 issue of the Internet Journal of Advanced Nursing Practice. Thyroid hormone deficiency causes many problems, such as lack of energy, weight gain, hair loss, dry skin and intolerance to cold. Eltroxin reverses these symptoms.

Eltroxin and Bone Mineral Density

Women are more likely to develop hypothyroidism than men are. Long-term Eltroxin use is associated with decreased bone mineral density in women. This is especially the case for postmenopausal women taking relatively high doses or in women taking Eltroxin to treat an enlarged thyroid gland, notes DailyMed, a website of the U.S. National Library of Medicine. One factor may involve increased serum levels of calcium and phosphorous and increased removal of these minerals through urine. Many patients taking levothyroxine also take a calcium supplement, according to the Internet Journal of Advanced Nursing Practice article.

Calcium and Eltroxin Absorption

To make matters more complicated, calcium supplements can lessen your body's absorption of Eltroxin. The supplements may reduce the bioavailability of levothyroxine by up to one-third, according to Drugs.com. This lowers the effectiveness of the thyroid hormone medicine. Researchers have not identified the precise way these two substances interact, but levothyroxine may adhere to calcium at acidic pH levels, creating a complex that is insoluble and poorly absorbed.


You can solve the Eltroxin and calcium interaction problem with timing. Take calcium supplements at least four hours before or after you take levothyroxine, advises Mayo Clinic endocrinologist Todd B. Nippoldt. The interaction is much weaker if you don't take the two close together. Be aware that in addition to supplements, calcium is a component of many antacids, and these antacids could also interfere with the effectiveness of your Eltroxin.

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