What are DRGs? Medicare Severity Diagnosis Related Groups, or MS-DRGs, are payment groups designed for Medicare beneficiaries. Patients who have similar clinical characteristics and similar treatment costs are assigned to an MS-DRG. The MS-DRG will be linked to a fixed payment amount based off the average treatment cost of patients in the group. Hospitals provide this information on their bills, and Medicare uses the information to decide how much the hospital should be paid.