Levothyroxine is sold under several brand names, including Synthroid, Levoxyl, Unithroid, and Levothroid.
Ageneric version of levothyroxineis also available.
But there is some controversy about whether it’s as effective and reliable as the brand-name versions.
Verywell / Emily Roberts
This article explains how the potency can vary between brand-name and generic versions of levothyroxine.
Most medications are available in brand-name and generic preparations.
Brand-name preparations are usually the first ones available on the market.
Get our printable guide for your next doctor’s appointment to help you ask the right questions.
After a period of time, other manufacturers are allowed to make generic versions of the same drug.
The brand-name preparations of levothyroxine available in the United States for the treatment of hypothyroidism have been thoroughly tested.
They are known to be reliable and effective.
Levothyroxine, however, is one of a handful of exceptions.
The versions differ in two key ways: potency and added ingredients (which are usually inactive).
The potency of one levothyroxine option may seem only slightly different from another.
That can dramatically influence your thyroid disease management.
Generic formulations tend to be less so.
Ingredients added to drugs are usually considered “inert” or “inactive.”
But studies have found that these inactive ingredients can sometimes decrease the effectiveness of a particular drug.
They could also pose problems for people with allergies or sensitivities.
In other words, Synthroid produced better results.
You may wish to ask your healthcare provider what they make of these reports.
The American Thyroid Association recommends taking the same brand-name (or generic) medication throughout your treatment.
Levothyroxine, however, is an exception.
Other people simply aren’t suited to the generic formulation, primarily because of pre-existing health issues.
To make the best decision, consult your healthcare provider.
You are more likely to experience ill effects by changing to a brand-name product.
Remember that no one knows your body like you do.
American Thyroid Association.Thyroid hormone treatment.
U.S. Food & Drug Administration.Generic drugs: Questions & answers.
U.S. Food & Drug Administration.Levothyroxine sodium product information.
National Institutes of Health.Hypothyroidism.
Pottel J, Armstrong D, Zou L, et al.The activities of drug inactive ingredients on biological targets.Science.
2017;51(8):640-648. doi:10.1177/1060028017705393
American Thyroid Association.What are the differences in thyroid preparations?
2013;98(2):610617. doi:10.1210/jc.2012-3125
American Thyroid Association.Q&A: Thyroxine preparations.
