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National (Nationwide) Inpatient Sample (NIS)

National Inpatient Sample (NIS)

What is the NIS?

The National Inpatient Sample (NIS) is part of the family of databases and software tools developed for the Healthcare Cost and Utilization Project (HCUP). The NIS is the largest all-payer inpatient care database in the United States, containing data on more than seven million hospital stays. Its large sample size is ideal for developing national and regional estimates, and it enables analyses of rare conditions, uncommon treatments, and special populations.

Advance Your Research

Apply more than 100 clinical and nonclinical variables to your research, including:
  • Primary and secondary diagnoses and procedures
  • Patient demographic characteristics
  • Hospital characteristics
  • Total charges
  • Expected payer
  • Discharge status
  • Length of stay
  • Severity and comorbidity measures
Address Critical Topics

The NIS can be used to study a variety of research topics, including: 
  • Access to care
  • Quality of care and patient safety
  • Use and cost of hospital services
  • Variations in medical practice
  • Health care cost inflation
  • Medical treatment effectiveness
  • Impact of health policy changes
  • Diffusion of medical technology
  • Regional and national analyses
  • Utilization of health services by special populations
A Comprehensive, User-Friendly Resource

The NIS is nationally representative of all short-term, non-Federal hospitals. It is sampled from hospitals that make up 97 percent of all discharges in the United States and includes all patients, regardless of payer. The vast size of the NIS allows the study of topics at both the national and regional levels. In addition, NIS data are standardized across years to facilitate ease of use.

Expand Your Analyses
    Use HCUP Tools. Free tools and software are available to estimate hospital costs, assess quality of care, and identify comorbidities. Most tools also can be used with other administrative health care databases.

    Make the Most of Your Research. HCUP Supplemental Files enhance applicable HCUP databases with additional data elements or analytically useful information. They cannot be used with other administrative databases.

    Explore NIS Data. HCUPnet ( is a free online query system that can provide you with instant access to health care statistics from HCUP databases, including the NIS.
Easy to Purchase

HCUP's Nationwide Databases are available for purchase from the online HCUP Central Distributor: The HCUP Central Distributor is the entity that accepts, processes, and fulfills applications for the purchase and use of HCUP databases.

The NIS is provided in ASCII format via secure digital download from the online HCUP Central Distributor. A statistical software package, such as SAS®, SPSS®, or Stata®, is required for analysis. Programs to load data into software packages are provided.

For a list of prices (including discounted student rates) and complete purchasing information, visit the HCUP-US website: This site also provides access to aggregate statistics from the NIS through the free online query resource known as the HCUPnet and contains detailed information about the Data Use Agreement, data elements, and software tools.

The Healthcare Cost and Utilization Project (HCUP, pronounced "H-Cup") is a family of powerful health care databases, software tools, and products for advancing research. Sponsored by the Agency for Healthcare Research and Quality (AHRQ), HCUP includes the largest all-payer, encounter-level collection of longitudinal health care data (inpatient, ambulatory surgery, and emergency department) in the United States, beginning in 1988.

HCUP is a Federal-State-Industry Partnership that brings together the data collection efforts of many organizations — such as State data organizations, hospital associations, private data organizations, and the Federal Government — to create a national information resource. HCUP would not be possible without the contributions of data collection Partners from across the nation.

For more information about HCUP, please visit

Internet Citation: National (Nationwide) Inpatient Sample (NIS). Healthcare Cost and Utilization Project (HCUP). May 2018. Agency for Healthcare Research and Quality, Rockville, MD.
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Last modified 5/17/18