WASHINGTON (WOWO): Patients across the country are raising concerns about unexpected medical bills after receiving additional charges known as facility fees for routine doctor visits.

Facility fees are extra charges some hospitals add for the use of their buildings, equipment, and support staff. The fees can apply even when a patient visits what appears to be a regular doctor’s office that is owned by a hospital system.

Patients say the charges can add hundreds of dollars to medical bills without clear warning. One Virginia woman says she received more than $300 in facility fees after routine appointments, despite expecting only her normal insurance co-pay.

Consumer advocates say hospitals should disclose these fees before appointments, including how much patients may owe and whether insurance will cover the charges.

Hospital officials say facility fees help support the cost of providing care and maintaining medical services, but acknowledge health care billing can be difficult for patients to navigate.

Advocates say more than 20 states have passed laws addressing facility fee transparency, but they argue additional protections are still needed.