Key takeaways
Synthroid is a brand-name version of levothyroxine, a thyroid hormone used to treat low thyroid hormone levels (hypothyroidism) and certain types of thyroid cancer. Both medications are taken once a day and work the same way in the body. But it isn't recommended to switch between them, as small differences in absorption can affect your thyroid levels. You'll typically receive regular blood tests to ensure your dosage is working well for you. You should take these thyroid medications on an empty stmoach, either first thing in the morning or before bed, at least 4 hours after your last meal or snack. Common side effects can include headache, trouble sleeping, and weight loss, but these usually occur if your dose is too high.
