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Medicaid Data

    • Owner / manager
    • Study and sample characteristics
    • Major foci
    • Special supplements and resources
    • Links to other datasets
    • Papers published
    • Dataset accessibility and cost
    • Help desk


Key web links

Home page
Data Available

MSIS data (summary state-level data, with options to create user-defined tables)


Other information from CMS:

Dataset Summary

Medicaid utilization and enrollment data files contain administrative data from the U.S. Medicaid program, including data on inpatient and outpatient health services utilization, long term care, and medications. Data files are very large and complex, and typically require an extensive investment of resources (for example, a statistical programmer with past experience using Medicaid data) to be used successfully. Summary files (which are much easier to use) are also available and provide state-level aggregated data on Medicaid enrollment and expenditures, drug utilization, and individual drugs covered under the Medicaid program.  Finally, users may drill down into state level data using the MSIS data mart, described below.

ResDAC suggests that users evaluate record layouts using information on the CMS MAX web site (provided above), since the ResDAC website is in need of updating.

Dataset Details

Dataset owner / manager 

Centers for Medicare and Medicaid Services

Study and sample characteristics   

Data includes information on all patients enrolled in the Medicaid program.  Data do not include information on patients eligible for Medicaid who are not enrolled in the program.

Data for years 1999 and beyond are included in the MAX file, which has 5 components:
-    Personal Summary File – includes demographic and enrollment data and a summary of utilization
-    Inpatient File – includes information on inpatient diagnoses, procedures, discharge status, length of stay, and payments
-    Long Term Care File – includes long term care services provided by Skilled Nursing Facilities, Intermediate Care Facilities, custodial (non-skilled) care facilities, and independent psychiatric facilities.
-    Drug File – includes information on drugs billed to Medicaid
-    Other Therapy File - includes claims data for non-institutional services including physician and other professional claims (regardless of setting).  Thus such claims include outpatient clinic visits (with diagnosis data), labs and X-rays, and payment information.

Major foci  

Medicaid data are claims data, and thus focus mostly on billable services. Main foci include:

-    Patient demographics
-    Inpatient and outpatient diagnoses (from billing information)
-    Health services utilization (from billing data of clinic visits, inpatient stays, procedures, lab and X-ray tests, etc.)
-    Medications (from billing information)

Special supplements and resources   

Aggregate data files (“Public Use Files”) are also available for state-level data on enrollment, expenditures, drug utilization, and more, and for information on covered drugs.  Unlike the MAX files, these are free and available for download without restriction.

MSIS data is state-level data, but access can be granted to the MSIS data mart, which allows the user to drill down to create more detailed and user-specific tables.  To request access to the mart, send an email to, including your contact information and reason for requesting access.

Information on MSIS data can be found at

Papers published  

Click here for a PubMed search for articles using this dataset.

Examples of papers published using Medicaid data include:

Prior authorization for antidepressants in Medicaid: effects among disabled dual enrollees.
Adams AS, Zhang F, LeCates RF, Graves AJ, Ross-Degnan D, Gilden D, McLaughlin TJ, Lu C, Trinacty CM, Soumerai SB.
Arch Intern Med. 2009 Apr 27;169(8):750-6.

Burden of concomitant asthma and COPD in a Medicaid population.
Shaya FT, Dongyi D, Akazawa MO, Blanchette CM, Wang J, Mapel DW, Dalal A, Scharf SM.
Chest. 2008 Jul;134(1):14-9.

Trends in emergency Medicaid expenditures for recent and undocumented immigrants.
DuBard CA, Massing MW.
JAMA. 2007 Mar 14;297(10):1085-92.

Medicaid prior-authorization programs and the use of cyclooxygenase-2 inhibitors.
Fischer MA, Schneeweiss S, Avorn J, Solomon DH.
N Engl J Med. 2004 Nov 18;351(21):2187-94.

Quality of care for medicaid-covered youth treated with antidepressant therapy.
Richardson LP, DiGiuseppe D, Christakis DA, McCauley E, Katon W.
Arch Gen Psychiatry. 2004 May;61(5):475-80.

Dataset accessibility and cost  

Requests for “Research Identifiable” (non-aggregated) data must be submitted through the Research Data Assistance Center (ResDAC).  After consultation with the researcher, access requests are forwarded to CMS for review.  Payment for data is required, and varies by the type of data requested.

Aggregate data is available for downloading for free from the CMS web site.

Help Desk  

Research Data Assistance Center (ResDAC)

Request a consultation (SGIM members only)
Members of SGIM may request a one-time consultation with an expert in this dataset, for example, to explore research ideas or to troubleshoot a problem or vexing question. Please click here for guidelines and the request process.