Is Generic Levothyroxine as Effective as Brand Name for Mild Thyroid Dysfunction?

For patients with mild thyroid dysfunction, initiating treatment with generic levothyroxine was found to be as effective as treatment with a brand-name product, according to a recently published retrospective cohort study.

The propensity score-matched longitudinal study aimed to compare the efficacy of generic and brand-name formulations of levothyroxine in achieving and maintaining target thyrotropin levels. The authors utilized the OptumLabs Data Warehouse administrative claims database to obtain laboratory data of commercially insured and Medicare Advantage enrollees in the United States. The study included patients 18 years of age and older who initiated generic or brand-name levothyroxine between January 1, 2008, and October 1, 2017, and who had thyrotropin levels between 4.5 and 19.9mIU/L.

In order to assess efficacy, the study authors determined the proportion of patients who initiated generic or brand-name levothyroxine and obtained a normal level of thyrotropin within 3 months, an abnormal thyrotropin level that was clinically meaningful within 3 months, and stable level(s) of thyrotropin within 3 months after falling into the normal range. 

The study included a total of 17,598 patients. During the study period, 15,229 patients filled generic levothyroxine prescriptions while 2229 filled brand-name prescriptions. The average (SD) age of the patients was reported to be 55.1 (16.0) years old, and 69.0% were female while 74.0% were White.

“Among 4570 propensity score–matched patients (mean [SD] age, 50.3 [13.8] years; 3457 [75.6%] female; 3510 [76.8%] White), the proportion with normal thyrotropin levels within 3 months of filling levothyroxine prescriptions was similar for patients who received generic vs brand-name levothyroxine (1722 [75.4%; 95% CI, 71.9%-79.0%] vs 1757 [76.9%; 95% CI, 73.4%-80.6%]; P =.23), as was the proportion with markedly abnormal levels (94 [4.1%; 95% CI, 3.4%-5.0%] vs 88 [3.9%; 95% CI, 3.1%-4.7%]; P =.65),” the study authors reported.

Additionally, the study authors observed that, among propensity score-matched patients who obtained a normal thyrotropin level within 3 months of initiation of therapy (n=1034), the proportion of patients receiving generic levothyroxine (n=427; 82.6%) who maintained normal levels of thyrotropin during the next 3 months was similar to that of those receiving brand-name levothyroxine (n=433; 83.8%) (P =.62).

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“This cohort study […] found that for adults with mild forms of thyroid dysfunction, consistent use of either the generic or brand-name formulations was associated with similar rates of achieving normal and stable thyrotropin levels,” the study authors concluded. They added, “Further research needs to clarify whether these findings are consistent among patients with no or little endogenous thyroid hormone production and whether switching between formulation affects these outcomes.”

Disclosure: Multiple authors declared conflicts of interest. Please refer to the original article for a full list of disclosures.


  1. Brito JP, Ross JS, Sangaralingham L, et al. Comparative effectiveness of generic vs brand-name levothyroxine in achieving normal thyrotropin levels [published online September 30, 2020]. JAMA Network Open. 2020;3(9):e2017645. doi:10.1001/jamanetworkopen.2020.17645.