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Levothyroxine vs Synthroid® – what is the difference? Knowing the answer to this question may help you save some money at the pharmacy. Although, both drugs are effective for treating multiple types of hypothyroidism since they contain the same active ingredient.


Levothyroxine belongs to a class of thyroid hormones and contains the active ingredient levothyroxine sodium.


Levothyroxine is used to treat multiple causes of underactive thyroid (hypothyroidism), as well as thyroid cancer and goiter (enlarged thyroid gland).


Like levothyroxine, Synthroid® belongs to a class of drugs named synthetic hormones. Its active ingredient is levothyroxine sodium, which replaces a hormone normally produced by the thyroid called thyroxine (T4). 


Synthroid® is used to treat hypothyroidism, thyroid cancer, and enlarged thyroid glands. Some research suggests that Synthroid® may be better at treating hypothyroidism than generic levothyroxine, but the evidence isn’t conclusive. 

Levothyroxine vs Synthroid – What is the Difference?

Overall, there is no significant difference between levothyroxine vs Synthroid®, other than the fact that Synthroid® is a popular brand name and levothyroxine is the generic version of the same drug (which means it is usually less expensive). Levothyroxine is also available under other brand names, including Tirosint® and Levoxyl®.

It’s up to you and your medical provider to decide which type of hypothyroid medication—levothyroxine or Synthroid® or something else—is best for your needs. The American Thyroid Association advises that the best individualized treatment for thyroid disease involves lifelong treatment using the same brand of thyroid medication.

Disclaimer: this article does not constitute or replace medical advice. If you have an emergency or a serious medical question, please contact a medical professional or call 911 immediately. To see our full medical disclaimer, visit our Terms of Use page.

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