Last week, Senator Bernie Sanders of Vermont, chair of the Senate health committee, called on a government watchdog to investigate why insurance companies are still charging women for birth control — a move that thrust access to contraceptives back into the spotlight.

In a letter to the Government Accountability Office, the senator noted that insurance companies were charging Americans for contraceptives that, under federal law, should be free — and that they were also denying appeals from consumers who were seeking to have their contraceptives covered. Some experts estimate that those practices could affect access to birth control for millions of women.

Since 2012, the Affordable Care Act has mandated that private insurance plans cover the “full range” of contraceptives for women approved by the Food and Drug Administration, including female sterilizations, emergency contraceptives and any new products cleared by the F.D.A. The mandate also covers services associated with contraceptives, like counseling, insertions or removals and follow-up care.

That means that consumers shouldn’t have any associated co-payments with in-network providers, even if they haven’t met their deductibles. Some plans might cover only generic versions of certain contraceptives, but patients are still entitled to coverage of a specific product that their providers deem medically necessary. Medicaid plans have a similar provision; the only exception to the mandate are plans sponsored by employers or colleges that have religious or moral objections.

Yet many insurers are still charging for contraceptives — some in the form of co-payments, others by denying coverage altogether.

A Quarter of Women Are Paying Unnecessarily for Contraceptives

In his letter, Senator Sanders cited a recent survey by KFF, a nonprofit health policy research organization, that found that roughly 25 percent of women with private insurance plans said they had paid at least some part of the cost of their birth control; 16 percent reported that their insurance plans had offered partial coverage, and 6 percent noted that their plans did not cover contraceptives at all. Additionally, a 2022 congressional investigation, which analyzed 68 health plans, found that the process to apply for exceptions and have contraceptives covered was “burdensome” for consumers and that insurance companies denied, on average, at least 40 percent of exception requests.