• Tue. Nov 28th, 2023

Healthcare Definition

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Diagnostic-Related Groups (DRG): Definition and More

A diagnostic-related group (DRG) is how Medicare (and some health insurance companies) categorize hospitalization costs to determine how much to pay for your hospital stay. Instead of paying for each individual service, a predetermined amount is set based on your diagnostic-related group.

The DRG is based on your primary and secondary diagnoses, comorbidities, age, sex, and necessary medical procedures. The system is intended to make sure that the care you need is the care you get, while also avoiding unnecessary charges.

This article discusses diagnostic-related groups. It explains how DRGs factor into Medicare payments and how DRGs may impact your care.

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What Are Diagnosis-Related Grouping (DRG) Systems?

Since the 1980s, the DRG system has included both:

  • An all-payer component for non-Medicare patients
  • The Medicare-Severity Diagnostic-Related Group (MS-DRG) system for Medicare patients

The MS-DRG system is more widely used and is the focus of this article.

MS-DRG System

Under Medicare’s DRG approach, Medicare pays the hospital a predetermined amount under the inpatient prospective payment system (IPPS). The exact amount is based on the patient’s DRG or diagnosis.

Long-Term Care

A different system called the Long-Term Care Hospital Prospective Payment System (LTCH-PPS) is used for long-term acute care hospitals. It’s based on different DRGs under the Medicare Severity Long-Term Care Diagnosis-Related Groups system (MS‑LTC‑DRGs).

How Do DRGs Work?

When you’re discharged from the hospital, Medicare will assign a DRG based on the main diagnosis that caused the hospitalization, plus up to 24 secondary diagnoses.

Every person is different, and two patients with the same condition might need very different types of care. That’s why the DRG can also be affected by your:

  • Primary diagnosis
  • Secondary diagnoses
  • Comorbidities
  • Necessary medical procedures
  • Age
  • Sex

How Payment Amounts Are Set

To determine DRG payment amounts, Medicare calculates the average cost of the resources needed to treat people in a particular DRG.

This base rate is then adjusted based on various factors, including the wage index for a given area. For example, a hospital in New York City pays higher wages than a hospital in rural Kansas, which is reflected in the payment rate each hospital gets for the same DRG. 

For hospitals in Alaska and Hawaii, Medicare adjusts the non-labor portion of the DRG base payment amount because of the higher cost of living. Adjustments to the DRG base payment are also made for teaching hospitals and hospitals that treat many uninsured patients.

The baseline DRG costs are recalculated annually and released to hospitals, insurers, and other health providers through the Centers for Medicare and Medicaid Services (CMS).

If the hospital spends less than the DRG payment on your treatment, it makes a profit. If it spends more than the DRG payment treating you, it loses money.

What Is Case-Mix Complexity? 

Case-mix complexity is used in tandem with DRGs. The term refers to distinct patient attributes that may affect the cost of care. These include: 

  • Severity of illness
  • Prognosis
  • Treatment difficulty
  • Need for intervention
  • Resource intensity

To healthcare providers, case-mix complexity refers to the patient’s condition and the type of treatment they need. To hospital administrators, it indicates the degree of resources needed and how much that will cost. Insurance regulators use these to determine how much they pay.

The phrase case-mix complexity is generally used to denote patients with a poor prognosis or greater severity of illness, treatment difficulty, or need for intervention.  

It factors in complications or comorbidities (CC) and can include hospital-acquired conditions, such as a surgical site infection or a pulmonary embolism following joint-replacement surgery.

What Is the History of the DRG System?

Before the DRG system was introduced in the 1980s, the hospital would send a bill to Medicare or your insurance company that included charges for every bandage, X-ray, alcohol swab, bedpan, and aspirin, plus a room charge for each day you were hospitalized.

This incentivized hospitals to keep you for as long as possible, perform as many procedures as possible, and use more supplies.

As health care costs increased, the government looked for ways to control costs while encouraging hospitals to provide care more efficiently. The DRG system is what resulted. Starting in the 1980s, DRGs changed how Medicare pays hospitals.

What Is the Impact of DRGs on Health Care?

The DRG payment system encourages hospitals to be more efficient and reduces their incentive to overtreat you. This has both benefits and drawbacks for patient care.


The DRG system is intended to standardize hospital reimbursement. The benefits of DRG are improved efficiency, reduced length of stay, and lower costs of treatment. 

Each DRG encompasses patients with clinically similar diagnoses whose care requires the same amount of resources to treat. A DRG also considers factors about the specific hospital, including:

  • Where a hospital is located
  • The type of patients the hospital treats
  • Other regional factors

For a patient, the DRG system makes it less likely for the hospital to order unnecessary tests. This can be both a positive and a negative. No one wants to undergo medical tests they don’t need, but the necessity of tests is determined by an administrative formula.

The other benefit to patients is a shorter hospital stay. The upside of this is no one enjoys being in the hospital, so an earlier discharge is typically welcome. The downside, however, is patients may be released too soon, increasing the odds of readmission.


The diagnostic-related grouping system also has its drawbacks. For patients, this includes:

  • Decreased quality of care
  • Upcoding or receiving a more severe diagnosis than necessary, which can cause undue worry and stress for patients and their loved ones
  • Dumping or being discharged too early or moved to a rehabilitation or long-term care facility too soon, as a way to save the hospital money
  • Increased odds of hospital readmission due to early discharge

For hospitals, the reimbursement methodology affects the bottom line. As a result, many private hospitals channel their resources to higher-profit services.

To counter this, the Affordable Care Act (ACA) introduced Medicare payment reforms, including bundled payments and Accountable Care Organizations (ACOs).

Still, DRGs remain the structural framework of the Medicare hospital payment system.

Discharge Rate

Hospitals are eager to discharge you as soon as possible and are sometimes accused of discharging people before they’re healthy enough to go home safely.

Medicare has rules that penalize a hospital in certain circumstances if a patient is readmitted within 30 days. This is meant to discourage early discharge—a practice often used to increase the bed occupancy turnover rate.

Outpatient Services

Hospitals are often eager to open beds for incoming patients. As a result, the hospital may discharge patients to an inpatient rehab facility or home with a visiting nurse service or other home health support.

Discharging patients sooner rather than later helps the hospital make a profit from the DRG payment. However, Medicare requires the hospital to share part of the DRG payment with the rehab facility or home healthcare provider to offset the additional costs associated with those services.

The IPPS payment based on your Medicare DRG also covers outpatient services that the hospital (or an entity owned by the hospital) provided in the three days leading up to the hospitalization.

Outpatient services are typically covered under Medicare Part B, but this is an exception to that rule, as the IPPS payments come from Medicare Part A.

Frequently Asked Questions

  • What is the benefit of diagnostic related groupings?

    The main benefits are increased efficiency, better transparency, and reduced average length of stay.

  • What is the difference between DRG, ICD, and CPT?

    These are all medical codes, but they each have different meanings:


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