Last Updated on December 18, 2025 by Melissa Lazaro

Why ISO/IEC 17043 vs ISO/IEC 17025 Still Causes Confusion

Here’s what I’ve noticed over the years.
Even experienced labs and quality managers mix these two standards up.

ISO/IEC 17025 and ISO/IEC 17043 often show up in the same conversations.
Audits. Accreditation. Proficiency testing.
So people assume they’re interchangeable. They’re not.

In my experience working with testing labs, calibration labs, and PT providers, this confusion leads to real problems.
Wrong accreditation scope.
Rejected applications.
Costly reassessments.

By the end of this article, you’ll clearly understand:

• What ISO/IEC 17025 actually covers
• What ISO/IEC 17043 is designed for
• When you need one, the other, or both
• How accreditation bodies look at each standard during audits

Now that we’ve set the stage, let’s break them down one by one.

ISO/IEC 17043 Explained: What Proficiency Testing Providers Actually Do

ISO/IEC 17043 is not a laboratory standard.
That’s the first thing to get straight.

This standard applies to proficiency testing (PT) providers.
These are organizations that design, run, and evaluate PT schemes for laboratories.

Their job isn’t to test samples for clients.
Their job is to check whether other labs are performing competently.

Key responsibilities under ISO/IEC 17043 include:

• Designing valid PT schemes
• Ensuring sample homogeneity and stability
• Applying correct statistical evaluations
• Protecting participant confidentiality
• Remaining impartial and independent

Here’s a common real-world issue I see.
A lab decides to run an interlaboratory comparison “internally” and calls it a PT scheme.
But there’s no statistical competence.
No documented scheme design.
No independence.

That’s where accreditation bodies step in and say, “This is ISO/IEC 17043 territory.”

Pro tip:
If you’re organizing PT or ILCs for external participants, ISO/IEC 17043 isn’t optional. It’s expected.

ISO/IEC 17025 Explained: Laboratory Competence in Practice

ISO/IEC 17025 is about one thing above all else: technical competence.

This standard applies to:

• Testing laboratories
• Calibration laboratories
• In-house labs supporting production or compliance

It focuses on whether your lab can produce valid, reliable results.

Core areas include:

• Method validation and verification
• Measurement uncertainty
• Traceability to SI units
• Equipment control and calibration
• Personnel competence
• Quality control and result reporting

In audits, assessors spend a lot of time here.
They don’t just read procedures.
They follow the data.

I’ve seen labs with beautiful manuals fail audits because the analysts couldn’t explain their methods or uncertainty calculations.

Pro tip:
ISO/IEC 17025 isn’t won on paper. It’s proven at the bench.

ISO/IEC 17043 vs ISO/IEC 17025: Scope and Purpose Compared

This is where the confusion usually clears.

ISO/IEC 17025 answers this question:
“Can this lab produce technically valid results?”

ISO/IEC 17043 answers a different one:
“Can this organization objectively evaluate the performance of other labs?”

Think of it this way:

• ISO/IEC 17025 = doing the testing
• ISO/IEC 17043 = evaluating the testers

They serve different roles in the conformity assessment ecosystem.

A lab can be accredited to ISO/IEC 17025 and still fail if it runs PT schemes without ISO/IEC 17043 controls.

That overlap is where many organizations stumble.

ISO/IEC 17043 vs ISO/IEC 17025 Requirements: Structural Differences That Matter

Both standards follow a similar high-level structure.
But the technical focus is very different.

ISO/IEC 17025 emphasizes:

• Analytical methods
• Measurement uncertainty
• Traceability and calibration
• Technical records

ISO/IEC 17043 emphasizes:

• PT scheme design
• Statistical methods
• Result evaluation criteria
• Handling outliers and non-participants

Here’s something I’ve seen repeatedly.
Organizations underestimate the statistical competence required for ISO/IEC 17043.
They assume basic spreadsheets are enough. They’re not.

Pro tip:
If statistics make your team uncomfortable, ISO/IEC 17043 will expose that quickly during assessment.

Do You Need ISO/IEC 17043, ISO/IEC 17025, or Both?

This depends entirely on what you do.

You likely need ISO/IEC 17025 only if:

• You perform testing or calibration for clients
• You participate in PT schemes but don’t organize them

You likely need ISO/IEC 17043 only if:

• You design and operate PT schemes
• You don’t provide routine testing services

You may need both if:

• You run a laboratory and offer PT schemes externally

I’ve worked with organizations that applied for the wrong standard first.
Six months later, they were back at square one.

Pro tip:
Before applying, map your actual activities—not what you call them internally.

ISO/IEC 17043 and ISO/IEC 17025 in Audits: What Assessors Really Look For

Assessors approach these standards very differently.

For ISO/IEC 17025, they:

• Observe testing
• Interview analysts
• Trace results back to raw data

For ISO/IEC 17043, they:

• Review PT scheme design
• Check statistical evaluations
• Verify impartiality and confidentiality

One common audit finding I see is role confusion.
The same person designing the PT scheme also evaluating results without safeguards.

That’s a red flag.

Pro tip:
Clear role separation saves a lot of audit pain.

FAQs: ISO/IEC 17043 vs ISO/IEC 17025

Is ISO/IEC 17043 mandatory for labs participating in proficiency testing?
No. Participant labs only need ISO/IEC 17025. ISO/IEC 17043 applies to PT providers, not participants.

Can an ISO/IEC 17025 accredited lab offer proficiency testing?
Yes, but only if it also meets ISO/IEC 17043 requirements for those PT activities.

Do accreditation bodies assess ISO/IEC 17043 and ISO/IEC 17025 differently?
Absolutely. ISO/IEC 17025 assessments focus on technical testing competence. ISO/IEC 17043 assessments focus on scheme design, statistics, and impartiality.

Conclusion: Choosing the Right Path Between ISO/IEC 17043 and ISO/IEC 17025

Let’s simplify it.

ISO/IEC 17025 proves your lab can test competently.
ISO/IEC 17043 proves you can evaluate other labs fairly and correctly.

They’re complementary. Not interchangeable.

If you’re unsure which applies to you, that’s normal.
Most organizations are closer than they think—but small misunderstandings cause big delays.

The smartest next step?
Run a focused gap analysis against your actual activities.
That clarity alone can save months of rework and reassessment.