Thyroid hormone medicine is the only effective way to treat hypothyroidism. In most cases, thyroid hormone medicine:

• Reduces or eliminates symptoms of hypothyroidism. Symptoms usually improve within the first week after you begin therapy. All symptoms usually disappear within a few months.
• May reduce the risk of slowed physical growth, mental retardation, and behavioral problems in infants and children.

Thyroid hormone medicine does not cause side effects if you take the correct dose.

Medication Choices

Thyroid hormone medicine, such as levothyroxine sodium (for example, Synthroid, Levoxyl, or Levothroid)

What To Think About

People who have hypothyroidism need treatment with thyroid hormone medicine. Depending on the cause of their hypothyroidism, they may need treatment for the rest of their lives.

Taking certain supplements, such as calcium or iron (or both), at the same time as thyroid hormone medicine may reduce the amount of thyroid hormone medicine absorbed by the body. Take calcium supplements at least 4 hours before or after taking thyroid hormone medicine.⁹ Also avoid taking iron supplements at the same time as thyroid medicine.

Talk to your doctor about whether you need to change your dose of thyroid medicine if you also take birth control pills or other hormones. You may need to take more thyroid hormone medicine than you would if you were not taking these hormones.¹⁰

Follow-up visits with your doctor are important to make sure that you are taking the correct dose of medicine. Most people return to their doctor for blood tests 6 to 8 weeks after starting treatment. After thyroid hormone levels return to normal, thyroid function tests are rechecked once a year.