Is levothyroxine safe for long-term use?

Levothyroxine is intended for long-term use. Most people who take levothyroxine for naturally occurring thyroid hormone deficiency need to take the medication for the rest of their lives. Postmenopausal women who take levothyroxine on a long-term basis can experience bone density loss, which can lead to osteoporosis. In these cases, doctors will prescribe the lowest effective dose of levothyroxine in order to minimize bone loss.