How to Read a Hospital Bill: CPT Codes Explained

The difference between a summary bill and an itemized bill

Most patients receive a summary bill — a document that says something like "Hospital Services: $8,400. Your portion: $1,200." This tells you almost nothing about what you were actually charged for, and it's nearly impossible to check for errors.

An itemized bill lists every single charge — every procedure, every supply, every medication — with the specific code and price for each. You are legally entitled to request one, and you should always do so before paying anything significant.

What is a CPT code?

CPT stands for Current Procedural Terminology. It's a standardized 5-digit code system maintained by the American Medical Association that describes virtually every medical procedure, test, or service a provider can perform.

Every line on your itemized bill should have a CPT code. These codes are not random — they're specific. CPT 99213 is a standard 15-minute office visit. CPT 71046 is a 2-view chest X-ray. CPT 36415 is a routine blood draw. The code tells you exactly what you were billed for.

Why does this matter? Because every CPT code has a published Medicare reimbursement rate. The CMS (Centers for Medicare & Medicaid Services) publishes the Physician Fee Schedule every year, listing what Medicare pays for each code. This serves as a national benchmark for fair pricing — and it's what BillScan AI checks your bill against.

Common CPT codes you might see on your bill

Medicare rates are for non-facility settings. Hospital rates will differ but these serve as a fair market benchmark.

What are ICD-10 codes?

Alongside CPT codes, your bill will also contain ICD-10 diagnosis codes — a separate system that describes why you received the service (the diagnosis), rather than what was done. ICD-10 codes start with a letter followed by numbers, like J06.9 (upper respiratory infection) or S93.401A (ankle sprain).

ICD-10 codes matter because insurers use them to determine whether a procedure was medically necessary. A wrong diagnosis code can turn a covered procedure into an uncovered one — and you'd get a bill for something insurance should have paid.

Understanding facility fees

If you visited a hospital-owned clinic or outpatient center, you may receive two separate bills: one from the physician (the professional fee) and one from the facility (the facility fee). This is called split billing, and it's legal — but many patients don't expect it.

Facility fees cover the cost of using the building, equipment, and nursing staff. They can be substantial — sometimes more than the physician's fee itself. Always check whether a clinic is hospital-affiliated before your visit, so you know to expect two bills.

What "adjustment" and "write-off" mean

If you have insurance, your EOB (Explanation of Benefits) will show a column called "adjustment," "write-off," or "contractual adjustment." This is the amount your provider agreed to accept as payment in full under their contract with your insurer — it's not a discount they're doing you a favor with, it's a pre-negotiated rate.

The amount remaining after the adjustment is split between what your insurance pays and what you owe (your deductible, copay, or coinsurance). If you're being asked to pay more than that remaining amount, something is wrong.

The fastest way to check if your bill is fair

Manually looking up every CPT code takes time and expertise. BillScan AI does it automatically — extract every code from your bill, compare each one against the official 2026 CMS Physician Fee Schedule, and flag any charges that look excessive. It also checks for duplicates, upcoding, and unbundling at the same time.