Diagnosis-Related Group (DRG)
A Diagnosis-Related Group (DRG) is the system Medicare and many other payers use to pay hospitals a fixed amount per inpatient stay. Each admission is assigned to a group of clinically similar, similarly resource-intensive cases, and the hospital is paid a set rate for that group regardless of the individual services delivered.
What is a Diagnosis-Related Group (DRG)?
A Diagnosis-Related Group (DRG) is a patient-classification system that sorts inpatient hospital stays into categories sharing similar diagnoses, procedures, and expected use of resources. Each category groups cases that should cost roughly the same to treat, and the payer reimburses one fixed, predetermined amount for the assigned group rather than itemizing every service.
Medicare introduced the approach for inpatient payment in the 1980s, and many other payers have adopted variations of it. The current Medicare version is the MS-DRG, which refines the original groups with severity tiers.
What is the full form of DRG?
DRG stands for Diagnosis-Related Group. The name reflects how the system works: inpatient cases are related to one another by diagnosis (along with procedures and severity) and grouped for payment. You will also see MS-DRG (Medicare Severity DRG) and AP-DRG (All-Patient DRG), which are variants of the same framework.
How is a DRG assigned?
Assignment is driven by coded clinical data. After discharge, the coded principal diagnosis, secondary diagnoses, procedures performed, and factors such as complications, comorbidities, age, and discharge status are run through standardized software called a grouper, which places the stay into exactly one DRG.
Each group carries a relative weight that, combined with the hospital's base rate, determines the payment for the entire stay. That makes documentation and coding precision directly financial: a missed complication or comorbidity can drop a case into a lower-paying group.
Why does the DRG model matter?
Because payment is fixed per group, the DRG system shifts financial risk toward providers and rewards efficient, well-coordinated inpatient care. If a stay costs less than the set amount, the facility benefits; if it costs more, the facility absorbs the difference.
The model also standardizes how case mix is measured. Metrics such as the case mix index are built on DRG weights, so the same classification that drives payment also describes how complex a hospital's patients are.
Do DRGs apply to ambulatory surgery centers?
No. DRGs are an inpatient construct, so they do not govern how an ambulatory surgery center is paid. Outpatient facilities are reimbursed under procedure-based systems instead — hospital outpatient departments under Ambulatory Payment Classifications (APCs), and ASCs under the Medicare ASC fee schedule and their contracted commercial rates, both keyed to the CPT codes of the procedures performed. You can browse which procedures are ASC-payable in our CPT code directory.
Understanding DRGs still matters for ASC and revenue-cycle teams, since DRG economics shape decisions about whether a case belongs in an inpatient or outpatient setting, and site-of-service shifts move volume between the two payment frameworks.
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