A hospital-acquired condition (HAC) is any medical condition or complication a patient develops during a hospital stay that was not present at the time of admission. The term has a specific meaning in the U.S. healthcare system: Medicare uses it to identify 14 categories of preventable conditions that hospitals should be able to avoid with proper care. When these conditions occur, they can extend a hospital stay by an average of 11 days and carry serious risks, including a nearly fivefold increase in the chance of dying compared to patients who don’t develop one.
How Medicare Defines HACs
The Centers for Medicare and Medicaid Services (CMS) maintains an official list of 14 categories of hospital-acquired conditions. To qualify for this list, a condition must meet two criteria: it must be reasonably preventable through evidence-based guidelines, and it must not have been present when the patient was admitted. That second point is critical. If you arrive at the hospital already showing signs of a condition, it doesn’t count as hospital-acquired, even if it worsens during your stay. Hospitals document what’s present on admission specifically to make this distinction.
The HAC designation isn’t just a label. It has direct financial consequences. Medicare will not pay hospitals the additional cost of treating a condition that the hospital itself caused. On top of that, the HAC Reduction Program penalizes the worst-performing hospitals (those scoring above the 75th percentile for HAC rates) with a 1% reduction in all their Medicare payments for the entire fiscal year. That across-the-board cut applies to every Medicare discharge, not just the cases where something went wrong.
The 14 Categories of HACs
The official CMS list covers a wide range of preventable problems, from infections to surgical errors to injuries sustained in the hospital. Here are the major categories:
- Foreign object retained after surgery, such as a sponge or instrument left inside the body
- Air embolism, where air enters the bloodstream through an IV line or surgical site
- Blood incompatibility, meaning a patient receives the wrong blood type during a transfusion
- Stage III and IV pressure ulcers, deep wounds that develop when patients lie in one position too long
- Falls and trauma, including fractures, dislocations, burns, crushing injuries, and head injuries that happen during the hospital stay
- Poor blood sugar control, covering diabetic emergencies like ketoacidosis and hypoglycemic coma
- Catheter-associated urinary tract infections, caused by urinary catheters left in place
- Bloodstream infections from IV lines, particularly central venous catheters
- Surgical site infections following heart bypass surgery, weight-loss surgery, orthopedic procedures, and cardiac device implantation
- Blood clots (deep vein thrombosis or pulmonary embolism) following knee or hip replacement
- Collapsed lung caused by the insertion of a central venous catheter
Some of these, like leaving a surgical instrument inside a patient, are sometimes called “never events” because they should never happen under any circumstances. Others, like urinary tract infections from catheters, are more common and require systematic prevention efforts rather than just individual vigilance.
How HACs Differ From Related Terms
Three terms often get used interchangeably but mean different things. A hospital-acquired condition is the broadest category and is defined by CMS for payment purposes. A healthcare-associated infection (HAI) is a subset of HACs that refers specifically to infections, such as catheter-related urinary tract infections, bloodstream infections from IV lines, surgical site infections, and infections caused by antibiotic-resistant organisms like MRSA and C. difficile. A “never event” is a patient safety incident considered so serious and so preventable that it should never occur, like wrong-site surgery or a retained foreign object. There is overlap between all three categories, but each serves a different purpose in how hospitals track, report, and get held accountable for patient safety.
How Common They Are
National efforts to reduce HACs have made measurable progress. Between 2010 and 2015, HAC rates dropped by just over 20% across U.S. hospitals. Between 2014 and 2016 alone, reduction efforts prevented roughly 8,000 deaths and saved an estimated $2.9 billion in healthcare costs. These improvements came largely from hospitals adopting standardized prevention protocols, sometimes called “care bundles,” that combine multiple evidence-based steps into routine practice.
Despite that progress, HACs remain a significant problem. When they do occur, the consequences are steep. One case-control study found that patients who developed a healthcare-associated infection stayed in the hospital an average of 20.3 days, compared to 8.7 days for similar patients without one. The mortality rate among infected patients was 17%, compared to 4.7% in the control group.
How Hospitals Are Required to Track Them
Hospitals don’t just self-report their HAC rates. They are required to submit infection data to the CDC’s National Healthcare Safety Network (NHSN), which serves as the national surveillance system. Acute care hospitals must report central line bloodstream infections, catheter-associated urinary tract infections, surgical site infections for certain procedures, and facility-wide rates of MRSA bloodstream infections and C. difficile infections. These reporting requirements have been phased in over time, starting in 2011, and now cover not just ICUs but also general medical and surgical wards.
Long-term care hospitals have their own set of reporting requirements. CMS uses the data from all these facilities to calculate performance scores, compare hospitals against each other, and determine which ones fall into the penalty zone under the HAC Reduction Program.
What This Means if You’re a Patient
Understanding HACs gives you context for some of the things that happen during a hospital stay that might otherwise seem routine or annoying. The nurse who repositions you every two hours is preventing pressure ulcers. The surgical team that counts instruments before closing an incision is guarding against retained foreign objects. The push to remove your urinary catheter as soon as possible is driven by strong evidence that every extra day with a catheter raises the risk of infection. A catheter-associated UTI, for example, requires that the catheter has been in place for more than two consecutive days before the infection even qualifies for tracking.
You can also look up how your hospital performs. CMS publicly reports HAC scores, and hospitals in the worst-performing quartile are identified. If you’re facing a planned surgery, especially a joint replacement, heart procedure, or abdominal surgery, checking your hospital’s infection and complication rates can help you make a more informed choice about where to have it done.