Healthcare Insights
Top clinical laboratories by medical lab procedure volume
Clinical medical laboratories are healthcare facilities that provide a wide range of laboratory procedures that help healthcare providers diagnose, treat, and manage patient health. These facilities may also be referred to as medical testing labs.
What role do clinical laboratories play in healthcare?
Clinical laboratories perform blood draws and tests on specimens collected from patients. They can be located within a hospital or outpatient clinic facility or be a free-standing location. Data reports from the laboratories are entered into a laboratory information system (LIS) which is a platform that processes, manages, and stores the patients’ lab data. The LIS can send orders for analysis, receive test orders, check test quality, track orders and results, and send results to EHR systems for providers and patients to access.
Clinical lab technicians, who collect and test patient samples, are a crucial part of the care team and help diagnose health conditions based on the test sample. Diagnostic laboratory corporations, as well as medical device and medical supply companies, use data on these lab facilities to understand their competitive landscape or discover new markets.
Below, we’ve listed the top 20 clinical medical laboratories in the U.S. by procedure volume using taxonomy code 291U00000X. The data is from the Atlas All-Payor Claims products for the calendar year 2025. The analysis excludes lab procedures performed in in-house labs, such as ones that are part of a hospital.
| Rank | Billing facility | NPI | City | State | % of 2025 lab procedures | Explore dataset |
|---|---|---|---|---|---|---|
| 1 | UNILAB CORPORATION | 1366479099 | WEST HILLS | CA | 9.6% | Explore |
| 2 | QUEST DIAGNOSTICS INCORPORATED | 1932145778 | CLIFTON | NJ | 7.8% | Explore |
| 3 | LABORATORY CORPORATION OF AMERICA | 1659352276 | SAN DIEGO | CA | 5.5% | Explore |
| 4 | QUEST DIAGNOSTICS CLINICAL LABORATORIES INC | 1891731626 | TAMPA | FL | 3.9% | Explore |
| 5 | QUEST DIAGNOSTICS CLINICAL LABORATORIES INC | 1518903350 | MIRAMAR | FL | 3.4% | Explore |
| 6 | QUEST DIAGNOSTICS LLC IL | 1881630614 | WOOD DALE | IL | 2.7% | Explore |
| 7 | QUEST DIAGNOSTICS LLC | 1952347791 | MARLBOROUGH | MA | 2.4% | Explore |
| 8 | LABORATORY CORPORATION OF AMERICA HOLDINGS | 1063497451 | RARITAN | NJ | 2.4% | Explore |
| 9 | QUEST DIAGNOSTICS CLINICAL LABORATORIES INC | 1790721538 | IRVING | TX | 2.2% | Explore |
| 10 | QUEST DIAGNOSTICS CLINICAL LABORATORIES INC | 1932166386 | TUCKER | GA | 2.2% | Explore |
| 11 | ACCU REFERENCE MEDICAL LAB, LLC | 1225110497 | LINDEN | NJ | 2.0% | Explore |
| 12 | LABORATORY CORPORATION OF AMERICA | 1255314704 | TAMPA | FL | 1.7% | Explore |
| 13 | UNILAB CORPORATION | 1619913449 | SACRAMENTO | CA | 1.5% | Explore |
| 14 | LABONE LLC | 1609812445 | LENEXA | KS | 1.5% | Explore |
| 15 | QUEST DIAGNOSTICS OF PENNSYLVANIA, INC. | 1841236684 | PITTSBURGH | PA | 1.5% | Explore |
| 16 | LABORATORY CORPORATION OF AMERICA | 1104829159 | BURLINGTON | NC | 1.4% | Explore |
| 17 | SHERMAN ABRAMS LABORATORY INC | 1598820235 | BROOKLYN | NY | 1.3% | Explore |
| 18 | QUEST DIAGNOSTICS INCORPORATED | 1043256886 | LAS VEGAS | NV | 1.2% | Explore |
| 19 | LABORATORY CORPORATION OF AMERICA HOLDINGS | 1538144910 | BURLINGTON | NC | 1.1% | Explore |
| 20 | SONORA QUEST LABORATORIES LLC | 1538105366 | PHOENIX | AZ | 1.1% | Explore |
Fig. 1 Data is from the Definitive Healthcare PhysicianView and Atlas All-Payor Claims products for calendar year 2025. Claims data is sourced from multiple medical clearinghouses in the U.S. and is updated monthly. Accessed June 2026.
What is the top clinical medical laboratory?
Unilab Corporation, headquartered in West Hills, California, was the clinical medical laboratory with the highest 2025 procedure volume, according to our data. This lab performed 9.6% of clinical laboratory procedures that were tracked.
In second place is the Quest Diagnostics Incorporated location in Clifton, New Jersey, which performed 7.8% of the lab procedures tracked in 2025. Laboratory Corporation of America’s San Diego facility came in third with 5.5% of total procedure volume.
The list of these 20 clinical medical laboratories is representative of where testing is billed and does not include collection sites. While laboratory testing is not exclusively performed in these clinical medical laboratories, these labs are the most prevalent vendors for handling large volumes of testing procedures.
Some laboratory companies including Quest Diagnostics, Laboratory Corporation of America, and Unilab Corporation operate multiple laboratory locations under different NPI numbers. As such, these companies appear multiple times on this list, and their listed procedure shares reflect individual locations rather than the entire company.
Learn more
Read about how medical device and medical supply companies use data from the Definitive Healthcare platform to better segment and target their healthcare accounts.
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