patient's share of medical costs; co-payment
Refers to the portion of medical expenses that the patient must pay out-of-pocket, as opposed to what is covered by insurance.
By using the high-cost medical expense benefit system, you can reduce the patient's share of costs.
自己負担 is a broader term for any out-of-pocket expense, while 患者負担 specifically refers to a patient's share of medical costs.
Compound of 患者 (patient) and 負担 (burden, share of costs).