Reducing Costs for Out-of-Network Services Act of 2019 This bill places limits on the cost to insurance plan holders for out-of-network health care services and on the amount charged for services provided to uninsured individuals. First, each state must select one of the following formulas for determining the maximum cost for a service: 125% of fee-for-service rate under Medicare, the 80th percentile of the cost for such service in the geographic area, or 100% of the allowed charges if the service had been provided in network. Health insurance issuers must set the cost-sharing amount for out-of-network services at no more than the state-selected rate for such service. Further, out-of-network health care providers may charge plan holders no more than the state-selected rate for a service. Each state also must set the maximum rate for services that health care providers may charge uninsured individuals at the lower of (1) 125% of the fee-for-service rate under Medicare, (2) the 80th percentile of the cost for such service in the geographic area, or (3) the rate otherwise applicable under state law. If a state does not select a maximum rate for a service provided to an insured or uninsured individual, the maximum rate a provider may charge is (1) 125% of the fee-for-service rate under Medicare, or (2) the rate established by the Department of Health and Human Services if such service is not covered under Medicare.