Hospital AI found $942 million worth of sicker patients — but nobody treated them any differently

A patient has major bowel surgery. A lab value comes back a little low, and software scanning the chart flags it: anemia. Nobody orders a transfusion. Nothing about the patient's care changes. But the new diagnosis can move the whole hospital stay into a higher billing tier — and the price moves with it.

That is the pattern the Blue Cross Blue Shield Association says it found across its claims data. In an analysis released on Thursday, the group estimated that hospitals coding patients as more complex added about $942 million in spending for Blue Cross and Blue Shield companies between 2023 and 2025. If you have ever paid coinsurance on a hospital stay, or opened a premium notice this fall, you have a stake in who is right.

How a diagnosis becomes a bigger bill

Most insurers pay for a hospital stay in bundles. Each stay is sorted into a diagnosis-related group — think of it as a price tag for "major bowel surgery" — and each group has tiers: without complications, with complications, with major complications. A secondary diagnosis, meaning a condition noted on top of the main reason you were admitted, can bump the stay up a tier.

That is where the software comes in. More than 60% of hospital systems now use AI tools that can read doctors' notes, lab reports and records to find conditions worth coding, according to the association. Some secondary diagnoses can be derived from a single lab value, which makes them, in the association's words, "particularly well-suited for detection by AI tools." About 70% of the extra cost — more than $650 million — traced back to those secondary diagnoses.

The tell: more diagnoses, same treatment

The association's argument rests on one comparison. If patients were truly sicker, you would expect them to get more treatment. "For example, we're seeing significantly more anemia diagnoses at these hospitals without a corresponding increase in transfusions," said Luke Chalker, the association's senior vice president of product and data science. "The disconnect between diagnoses and treatment suggests that AI is identifying more billable conditions, not sicker patients."

Among bowel surgery patients, reported partial intestinal blockages rose 55% from early 2023 to late 2025, Techstrong.ai reported from the analysis. At least one health system has been open about the upside: Michigan's McLaren Health Care has said it uses AI documentation to boost revenue by about $1 million a month, according to the same report.

The hospitals' side — and the insurers' glass house

Hospitals reject the framing. The American Hospital Association has said coding intensity also reflects patients who are older and sicker, and hospitals documenting real conditions more accurately; it points to a roughly 5% rise in case mix — the average complexity of patients — from 2019 to 2024. The group also noted, fairly, that insurers are not strangers to this game: the Medicare Payment Advisory Commission found in 2025 that coding by Medicare Advantage plans contributed to about $40 billion in overpayments.

Keep in mind who wrote the study. This is an insurer trade group's analysis of its own claims, released while insurers and hospitals fight over every dollar — often with dueling AI tools of their own, one side flagging diagnoses and the other flagging claims to deny. It is a data point, not a verdict. But "more diagnoses, same care" is a question the hospitals have not answered with data of their own.

Why this lands on you

Nearly $1 billion in two years does not vanish into a ledger. The association says it drives "higher premiums and out-of-pocket costs for families, employers and taxpayers," and on this point it is simply describing how insurance works: claims costs become next year's premiums. More directly, if your plan charges coinsurance — a percentage of the allowed amount — a stay billed in a higher tier means a higher share for you, up to your out-of-pocket maximum. Our guide to the deductible vs. out-of-pocket max explains where that ceiling sits.

There is a quieter cost too. A diagnosis coded for billing becomes part of your medical record, and it can follow you to the next doctor.

What to actually do after a hospital stay

• Ask for an itemized bill with the codes. Request the diagnosis codes and the diagnosis-related group the hospital billed. You are entitled to know what you are being charged for.
• Match it against your explanation of benefits. The EOB your insurer sends shows what was billed, what was allowed and what you owe. Our guide to reading an EOB walks through it line by line.
• Question diagnoses you never heard about. If the bill lists a condition nobody mentioned to you, ask the hospital's billing office — and your doctor — what it was based on and whether anything was done about it.
• Get your records. Under federal law you have a right to a copy of your chart, which is where a coded condition should be documented. See our guide to getting your medical records.
• If something looks wrong, ask your insurer for a claim review. They have every incentive to listen.

Whether the software is catching real illness or inventing billable paperwork, one thing is settled: a machine is now reading your chart for money. It is worth having a human — you — read the bill.