Health insurers limit access to drugs in several ways: they may exclude drugs from formularies or impose utilization management, such as prior authorization or step therapy, for covered products.
A study published online on July 9, 2026 in JAMA that investigated how frequently prescriptions are rejected because of insurance formulary restrictions in the United States, and how often the rejected medicines are ultimately dispensed, found that “(f)ormulary-based prescription rejections are frequent, increasing, and often consequential for patients’ access to prescribed therapies. Across payer types, these policies commonly result in delayed or absent treatment rather than timely substitution.”
Specifically, the study determined that of approximately 1.17 million individuals attempting to fill more than 2 million single-source branded drugs between 2018 and 2024, 32.0% were rejected. Once rejected, 38.6% of individuals obtained the prescribed drug, 13.0% received a medication in the same therapeutic class, and nearly half (48.4%) received no medication in the same therapeutic class within 90 days.
“These findings have several implications for policymakers, prescribers, and patients. First, the 67.4% documented increase in formulary rejections from 2018 to 2024 (from 24.3% to 40.7%), largely driven by prior authorization and step therapy requirements, signals a continued shift toward more utilization management of covered drugs in the United States rather than formulary exclusion alone. While this may also partly reflect changes in the mix of products entering the sample over time, it nevertheless indicates a rising administrative burden that prescribers and patients must navigate, even for covered products.
Second, differences in regulatory environments across insurance markets contribute to significant variation in how often products are rejected due to formulary. For example, while Medicaid can have Preferred Drug Lists, in which certain products are preferred to others, the program is generally required to cover all drugs if they are prescribed for a medically accepted indication. Unsurprisingly, while rejections remained common in Medicaid, this study found that they predominantly reflected utilization management restrictions.
Third, nearly half of patients included in this analysis received no medication in the same therapeutic class within 90 days following a rejection, while the remainder either ultimately filled the originally prescribed medicine (38.6%) or another medication in the same class (13.0%). These findings suggest that formulary-based rejections may not result in prompt substitution with therapeutic substitutes and are often associated with delays in treatment initiation. At the same time, medications from different therapeutic classes may represent appropriate substitutes in many circumstances—for example, when guidelines recommend a particular sequence of therapies or when prescribers select alternatives with different mechanisms of action but similar indications. Because this analysis focuses on dispensing of the originally prescribed drug or another medication within a fairly stringent class definition, we cannot determine the extent to which patients initiated treatment with clinically appropriate alternatives from other classes. However, the sensitivity analysis using a less stringent definition of therapeutic class yielded substantively similar findings to the primary analysis.”
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