ISO 15189 Accreditation: Requirements, Audits, and How It Differs from CLIA and ISO 17025

ISO 15189 is the international standard Medical laboratories — Requirements for quality and competence, published by the International Organization for Standardization (ISO). The current edition is ISO 15189:2022, which replaced the 2012 edition. It is the accreditation standard specific to medical (clinical) laboratories — the labs that examine biological specimens from humans for diagnosis, monitoring, treatment, or screening — and it is the standard a procurement officer, lab director, or hospital administrator should expect to see referenced when evaluating a clinical lab’s or reference lab’s quality credentials.

Like ISO/IEC 17025, ISO 15189 is granted as an accreditation, not a “certification.” A laboratory is accredited to ISO 15189 for a defined scope of examinations (specific analytes, methods, and specimen types), not certified as an organization in general. Any claim of ISO 15189 accreditation should be checked against the issuing accreditation body’s published scope of accreditation — see our guide to ISO/IEC 17025 for how scope-of-accreditation works in more detail, since the mechanism is the same across both standards.

What ISO 15189 covers

ISO 15189 sets requirements across the full path of a medical laboratory examination, organized into two main parts:

• General and management requirements — governance and impartiality, confidentiality of patient information, document control, risk management, internal audit, management review, and continual improvement of the quality management system.
• Technical requirements — personnel competence, facilities and environmental conditions, equipment, reagents and consumables, and, distinctively, the three-phase examination process: pre-examination (specimen collection, handling, and transport), examination (the analytical process itself, including method validation/verification and measurement uncertainty), and post-examination (result review, reporting, and retention of samples and records).

Two features distinguish ISO 15189 from a general testing/calibration standard: explicit requirements for point-of-care testing (POCT) oversight, and a strong emphasis on patient safety and the interpretive/reporting side of results, not just analytical accuracy. Reference intervals, critical-result notification, and turnaround-time management are all in scope in a way they are not for a general materials-testing lab.

ISO 15189 vs. ISO/IEC 17025: which standard applies

Both standards share a common lineage — ISO 15189 was originally developed as a medical-laboratory-specific adaptation of ISO/IEC 17025’s competence requirements, layered with ISO 9001-style quality-management principles and medical-specific requirements. For a buyer or lab director, the practical distinction is scope of applicability, not rigor:

• ISO 15189 applies to laboratories examining biological specimens from humans for clinical/diagnostic purposes — hospital labs, clinical reference labs, and point-of-care testing programs.
• ISO/IEC 17025 applies to testing and calibration laboratories generally — environmental, forensic, materials, and industrial testing labs, among others. Some clinical-adjacent labs (e.g., certain forensic toxicology or environmental-testing operations) are accredited to 17025 rather than 15189 because their work isn’t diagnostic patient testing.

If you are procuring or evaluating a laboratory whose output feeds a clinical decision, ISO 15189 (or, in the US, a nationally recognized clinical-lab accreditation such as CAP accreditation) is the relevant credential to require — not a bare ISO/IEC 17025 scope, which does not carry the medical-specific pre/post-examination and patient-safety requirements.

Who accredits to ISO 15189

ISO itself does not accredit laboratories. Accreditation is granted by a national or regional accreditation body, which is itself peer-evaluated for competence by the International Laboratory Accreditation Cooperation (ILAC) and, for signatories, covered by the ILAC Mutual Recognition Arrangement (MRA) — the mechanism that lets an ISO 15189 accreditation issued in one country be recognized internationally. Bodies that accredit medical laboratories to ISO 15189 include:

• UKAS (United Kingdom Accreditation Service) — the sole national accreditation body for the UK; ISO 15189 accreditation via UKAS is a requirement for NHS pathology laboratories.
• CAP (College of American Pathologists), in the United States — CAP offers an ISO 15189-based accreditation option alongside its own long-standing CAP Laboratory Accreditation Program checklist system; see our CAP accreditation checklist guide for how that program is structured.
• A2LA (American Association for Laboratory Accreditation) and other ILAC-affiliated national accreditation bodies also operate ISO 15189 programs in various countries; see our A2LA accreditation guide and ANAB accreditation guide for how those bodies’ scopes and processes work generally.

Before accepting an ISO 15189 accreditation claim from a supplier, reference laboratory, or diagnostic partner as part of a procurement or vendor-qualification decision, verify the accrediting body’s own public accreditation register or scope document rather than relying on a certificate alone — scopes are examination-specific and can lapse, be suspended, or be narrower than a vendor’s marketing implies. See our guide to the vendor qualification process for how to build that verification step into a broader supplier-evaluation workflow.

ISO 15189 vs. CLIA (United States)

In the US, these operate on different legal footing and buyers evaluating a domestic clinical lab need to understand both:

• CLIA (Clinical Laboratory Improvement Amendments, 42 CFR Part 493) is a mandatory federal regulatory requirement — any US laboratory testing human specimens for the diagnosis, prevention, or treatment of disease, or for health assessment, must hold a CLIA certificate, administered by CMS.
• ISO 15189 is a voluntary accreditation that demonstrates conformance to an international quality-and-competence standard. It does not replace CLIA certification, but CMS recognizes certain accreditation organizations (including CAP) as having “deemed status” — meaning a lab accredited through one of those recognized programs is treated as meeting CLIA’s quality requirements without a separate direct CMS/state survey. Confirm current deemed-status recognition directly with CMS or the accrediting body before relying on it for a compliance decision, since recognized-organization status can change.

What an ISO 15189 audit involves

Accreditation follows the same general lifecycle used across ISO/IEC 17011-based accreditation programs (the standard that governs how accreditation bodies themselves operate):

1. Application and document review — the laboratory submits its quality manual, defined scope of examinations, and supporting procedures for the accreditation body’s initial review.
2. Initial on-site assessment — assessors (typically including a technical assessor with relevant discipline expertise) evaluate the laboratory against ISO 15189’s management and technical requirements, including witnessing examinations, reviewing personnel competency records, equipment calibration/maintenance records, and pre/post-examination process controls.
3. Corrective action for nonconformities — findings are typically graded by severity; the lab must submit and, for higher-severity findings, demonstrate implemented corrective action before accreditation is granted.
4. Ongoing surveillance — accredited laboratories undergo periodic surveillance assessments and full reassessment on a defined cycle (accreditation bodies typically set this on an annual-surveillance/multi-year-reassessment pattern; the exact cadence is set by the specific accreditation body, not by ISO 15189 itself).
5. Ongoing quality-system evidence — between assessments, the lab is expected to maintain evidence such as internal audits, management review, and participation in proficiency testing / external quality assessment for accredited examinations.

Why this matters for procurement and vendor evaluation

For a lab manager or research administrator evaluating a reference laboratory, diagnostic testing vendor, or clinical-trial central lab, ISO 15189 accreditation status is a genuine, verifiable evaluation criterion — not a marketing claim to take at face value. Practical evaluation steps:

• Confirm scope, not just the credential. Request the vendor’s current scope of accreditation and check that the specific analytes/examinations you need are actually listed, not just that the organization holds “ISO 15189 accreditation” somewhere in its portfolio.
• Verify against the issuing body’s public register rather than a PDF certificate supplied by the vendor.
• Check accreditation status and dates — suspended, withdrawn, or expired accreditations happen, and a stale certificate is a real procurement risk.
• Ask how the vendor sources consumables and reagents that feed accredited examinations — a lab’s accreditation is only as reliable as its supply chain’s traceability and documentation; distributors and suppliers in this space (for example lac.us, a laboratory products distributor) are one part of that broader supply chain a procurement review may need to trace, alongside the lab’s own accreditation record.
• Where CLIA applies (US domestic testing), confirm CLIA certificate status separately — ISO 15189 accreditation and CLIA certification answer different questions and neither substitutes for verifying the other where both are legally or contractually required.

Frequently asked questions

What is ISO 15189 medical laboratory accreditation?

ISO 15189 medical laboratory accreditation is formal recognition, granted by a national accreditation body, that a clinical/medical laboratory meets the ISO 15189 standard’s requirements for quality management and technical competence across the pre-examination, examination, and post-examination phases of testing human biological specimens. It is granted for a defined scope of examinations, not as a blanket organizational certificate.

What are the requirements for ISO 15189?

ISO 15189 requirements fall into general/management requirements (governance, document control, risk management, internal audit, management review) and technical requirements (personnel competence, facilities/environment, equipment, and the pre-examination/examination/post-examination process controls described above, including method validation, measurement uncertainty, and point-of-care testing oversight where applicable).

What is the ISO 15189 standard used for?

It is used by medical laboratories — hospital labs, independent clinical reference labs, and point-of-care testing programs — to demonstrate, through third-party accreditation, that their examination processes and results are reliable and fit for clinical use, and by hospitals, health systems, and procurement teams as an evaluation criterion when selecting or auditing a clinical testing partner.

What happens in an ISO 15189 audit?

An accreditation body’s assessors conduct document review and an on-site assessment against the standard’s management and technical requirements, including observing examination processes, reviewing personnel and equipment records, and checking pre/post-examination controls; any nonconformities require corrective action before accreditation is granted or maintained, and accredited labs undergo periodic surveillance and reassessment on a cycle set by the accreditation body.