How Hospitals Calculate What They Charge You: The Inpatient Prospective Payment System

What Inpatient Prospective Payment Actually Is

Inpatient Prospective Payment is the system Medicare uses to decide how much it will pay a hospital for your stay. Instead of paying whatever the hospital charges, Medicare assigns a fixed dollar amount based on your diagnosis and the procedures you receive. The hospital gets that amount whether your actual care costs more or less. This system has been in place since 1983 and affects how much you may owe out of pocket, because your hospital bill often depends on what Medicare decides to pay first.

The key word is "prospective"—the payment is set before you are treated, not after. A hospital knows in advance that a patient admitted with pneumonia and no complications will generate a certain payment from Medicare. If that patient needs a ventilator or develops sepsis, the payment may shift to a higher category, but the hospital still cannot charge Medicare more than the system allows. This creates a direct link between your diagnosis code and your bill.

You need to understand this system because it shapes three things: what your hospital charges you, whether your bill seems to match your actual care, and why hospitals sometimes push back on certain treatments or discharge you quickly. The system is also why your bill may look completely different from someone else's, even if you were both hospitalized for similar reasons.

Key Takeaways

• Medicare pays hospitals a fixed amount per stay based on your diagnosis and procedures, not on how long you stay or what tests you receive.
• Your diagnosis is coded into a category called a Diagnosis-Related Group (DRG), and that code determines the payment amount.
• Hospitals bill you for the portion Medicare does not cover, so understanding your DRG helps you predict what you might owe.
• If you believe your diagnosis was coded incorrectly, you can request your medical records and ask the hospital to review the coding.
• This system applies only to Medicare; private insurance and Medicaid use different payment methods.

How the DRG System Sorts Your Hospital Stay Into a Payment Category

When you are admitted to a hospital, the medical records team assigns your stay a Diagnosis-Related Group (DRG) code. This code is built from three pieces of information: your primary diagnosis (why you came in), any secondary diagnoses (other conditions you have), and the procedures performed. The hospital's billing department uses this code to look up the payment amount Medicare will send.

Each DRG has a weight—a number that represents how resource-intensive that diagnosis typically is. A simple appendectomy might have a weight of 0.9, meaning Medicare pays 90 percent of a base amount. A complex cardiac surgery with complications might have a weight of 3.5, meaning Medicare pays 350 percent of that same base amount. The base amount itself changes every year and varies by region and hospital type.

The coding is not random. Hospitals employ coders—people trained to read your medical record and translate it into the correct diagnosis and procedure codes. If your coder misses a secondary diagnosis or codes your primary diagnosis at the wrong severity level, your DRG changes and so does the payment. This is why hospitals have financial incentive to code accurately and completely—but also why errors happen.

What You Owe After Medicare Pays Its Share

Medicare's payment to the hospital is not your bill. It is the hospital's revenue for your stay. You are responsible for your deductible (the amount you must pay before Medicare coverage kicks in), your coinsurance (a percentage of the hospital's charges after the deductible), and any charges the hospital cannot bill to Medicare.

For an inpatient hospital stay in 2024, Medicare beneficiaries typically owe a deductible of around $1,600 for the first 60 days, though this amount changes annually. After that, you may owe coinsurance—usually a daily amount for days 61 through 90, and a higher daily amount for days 91 and beyond. The exact amounts depend on the current year's Medicare rates.

The hospital's actual charges may be much higher than what Medicare pays. If a hospital's charge for your stay is $50,000 but Medicare's DRG payment is $20,000, the hospital absorbs the difference—they cannot bill you for it. However, if you have a supplemental insurance policy or if you are uninsured, the hospital may bill you differently. This is why your bill can look shocking even after Medicare pays.

Why Hospitals Discharge You Quickly Under This System

Because the hospital receives a fixed payment regardless of how many days you stay, there is financial pressure to discharge you as soon as medically safe. A patient who stays five days generates the same DRG payment as a patient who stays ten days. The hospital's costs for those extra five days come out of their revenue. This is not necessarily bad—it can mean faster recovery and fewer hospital-acquired infections—but it is worth knowing why the pressure exists.

You may notice that discharge planning starts early, that you are encouraged to move to a rehabilitation facility or home care, or that your doctor seems eager to send you home. This is partly because of the DRG system. If you believe you need more time in the hospital, you have the right to request a review. Medicare has a process called Quality Improvement Organization (QIO) review that allows you to challenge a discharge decision. Your hospital should provide you with notice of your discharge rights and information about how to request a QIO review.

How to Check Your Diagnosis Code and Spot Errors

You can request a copy of your medical records, including your discharge summary and billing codes, from the hospital's medical records department. Look for your primary diagnosis and any secondary diagnoses listed. If you know your medical history well, you may spot something wrong—a condition that was not treated, a procedure that was not listed, or a severity level that does not match what happened.

Common coding errors include missing secondary diagnoses (like diabetes or heart disease that affected your care), incorrect procedure codes, or wrong severity indicators. If you spot an error, contact the hospital's billing or medical records department in writing and explain what you believe is wrong. Include a copy of your discharge summary or medical records that support your correction. The hospital is required to review your request, though they are not required to change the code unless they agree an error occurred.

If the hospital refuses to correct what you believe is a genuine error, you can file a complaint with your state's health department or with the Centers for Medicare & Medicaid Services (CMS). These complaints do not change your current bill, but they create a record that may lead to broader audits of the hospital's coding practices.

The Difference Between Medicare Inpatient Payment and Other Insurance

Private insurance companies do not use the DRG system. They negotiate their own payment rates with hospitals, which may be higher or lower than Medicare's. Medicaid, the joint federal-state program for low-income people, uses its own payment methods—some states use DRGs similar to Medicare's, while others use different systems entirely. Veterans Administration hospitals use yet another system. This means your bill and your out-of-pocket cost depend heavily on which insurance you have.

If you are uninsured, the hospital will bill you at its full charge amount, which is typically much higher than what any insurer pays. Many hospitals have financial assistance programs for uninsured patients, and you should ask about these before or immediately after admission. Some hospitals are required by law to offer a discount or payment plan based on your income.

What Happens If You Disagree With Your Hospital Bill

A hospital bill is not final the moment you receive it. You can request an itemized bill that breaks down every charge by department and service. Compare this to your medical records—did you receive all the services listed? Were you charged for duplicate tests? Were you charged for services you refused?

If you find errors, send a written dispute to the hospital's billing department with copies of supporting documents. Keep records of all correspondence. If the hospital does not respond or you remain unsatisfied, you can file a complaint with your state's attorney general's office or your state's health department. You can also contact a patient advocate or billing advocate, many of whom work on contingency and take a percentage of any overcharge they recover.

Frequently Asked Questions

Can I find out my DRG code before I am discharged?

Yes. Ask the hospital's billing or medical records department for your DRG code and the payment amount Medicare assigned. They may not have finalized it yet if you are still an inpatient, but they can usually give you the preliminary code. Knowing this number helps you understand what your out-of-pocket costs are likely to be.

Does the DRG system apply to emergency room visits?

No. Emergency room visits are paid differently—usually as outpatient services. The DRG system applies only to inpatient hospital stays, meaning you were admitted and stayed at least one night. If you come to the ER and go home the same day, you receive an outpatient bill instead.

What if my hospital stay crosses into a new calendar year?

Your deductible and coinsurance amounts are based on the year in which you were admitted. If you are admitted in December and discharged in January, your entire stay uses the deductible and coinsurance rates from the year you were admitted. This can matter if rates change significantly between years.

Can I negotiate my hospital bill if I am insured?

You can always ask. Many hospitals will negotiate or offer a discount, especially if you pay a lump sum rather than setting up a payment plan. The worst they can say is no. If you are struggling to pay, ask about the hospital's financial assistance program—many have income-based programs that reduce or eliminate your bill.

Who decides what my secondary diagnoses are?

The hospital's coders decide, based on what is documented in your medical record. If your doctor did not write it down, the coder cannot code it. This is why it matters to tell your doctors about all your health conditions during admission—the more complete your medical record, the more accurate your coding is likely to be.