DRG 101: What Is a DRG and How Does It Work?

While DRGs may seem like a secret code used to make hospital bills more confusing, you can understand them if you have the right information. Yamada Taro/Getty Images

A DRG, or diagnostic related grouping, is how Medicare and some health insurance companies categorize hospitalization costs and determine how much to pay for a patient's hospital stay. Rather than paying the hospital for what it spent caring for a hospitalized patient, Medicare pays the hospital a fixed amount based on the patient’s DRG or diagnosis.

If the hospital treats the patient while spending less than the DRG payment, it makes a profit.

If the hospital spends more than the DRG payment treating the patient, it loses money.


Years ago, when you stayed in the hospital, the hospital would send a bill to Medicare or your insurance company that included charges for every Band-Aid, X-ray, alcohol swab, bed pan, and aspirin, as well as a room charge for each day you were in the hospital. This encouraged hospitals to keep you in hospitalized for as long as possible and to do as much to you as possible while you were in the hospital. After all, the longer you were in the hospital, the more money the hospital made on room charges. The more procedures you had done while hospitalized, the more Band-Aids, X-rays, and alcohol swabs you used.

As health care costs went up, the government sought a way to control costs while encouraging hospitals to provide care more efficiently. What resulted was the DRG.

DRGs changed how Medicare pays hospitals.

Instead of paying for each day you’re in the hospital and each Band-Aid you use, Medicare pays a single amount for your hospitalization based on your diagnosis.

An Example of How a DRG Works

A simplified version goes like this: Mr. Koff and Mr. Flemm were both admitted to the same hospital for treatment of pneumonia.

Mr. Koff was treated and released in 2 days. Mr. Flemm’s hospitalization lasted 10 days.

Since Mr. Koff and Mr. Flemm have the same diagnosis, they have the same DRG. Based on that DRG, Medicare pays the hospital the same amount for Mr. Koff as it does for Mr. Flemm even though the hospital spent more money providing 10 days of care to Mr. Flemm than providing 2 days of care to Mr. Koff.

With a DRG, Medicare pays for a hospitalization based on the diagnosis the patient was hospitalized to treat, not based on how much the hospital did to treat the patient, how long the patient was hospitalized, or how much the hospital spent caring for the patient.

In the case of Mr. Koff, the hospital may have made a small profit. The DRG-based payment was probably a little bit larger than the actual cost of Mr. Koff's two-day stay.

In the case of Mr. Flemm, the hospital probably lost money. It surely cost the hospital more to care for Mr. Flemm for 10 days than the DRG-based payment it received. 

The Impact of DRGs

The DRG system of payment encourages hospitals to become more efficient in treating patients and takes away the incentive for hospitals to over-treat patients. However, this is a two-edged sword as hospitals are now eager to discharge patients as soon as possible and are sometimes accused of discharging patients home before they’re healthy enough to go home safely.

Now Medicare has rules in place that punish a hospital financially if a patient is re-admitted to the hospital with the same diagnosis within 30 days of discharge. This is meant to discourage hospitals from discharging patients before they’re healthy enough to be discharged.

Additionally, in some DRGs, the hospital has to share part of the DRG payment with the rehab facility or home health care provider if it discharges a patient to an inpatient rehab facility or with home health support.

Since a patient can be discharged from the hospital sooner with the services of an inpatient rehab facility or home health care, the hospital is eager to do so because it's more likely to 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 health care provider to offset the additional costs associated with those services.

See a List of DRGs

If you’d like to see a list of Medicare’s MS-DRGs you may download a copy following these instructions:

  1. Go to the Final Rule Tables page on the CMS website.
  2. Scroll down to the area titled “Downloads.”
  3. Download table 5.
  4. Open the file that displays the information as an Excel spreadsheet (the file that ends with “.xlsx”.)

Learn More About DRGs

How Is Your DRG Determined?

How Does a DRG Determine How Much a Hospital Gets Paid?

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