Measurement Uncertainty
TestingAlso known as: MU, Uncertainty of Measurement, Analytical Uncertainty, Test Result Uncertainty
The range within which a test result's true value lies, reported alongside results.
What It Means
Measurement uncertainty quantifies the doubt associated with a test result. When a lab reports 'Vitamin D3: 1050 IU per serving ± 105 IU,' the ±105 IU is the measurement uncertainty — it means the true value is expected to fall between 945 and 1155 IU with a stated level of confidence (typically 95%). ISO 17025 clause 7.6 requires laboratories to evaluate and report measurement uncertainty where relevant. Reporting MU matters for supplement testing because it determines whether a product truly meets its label claim. A potency result of 98% with ±10% uncertainty means the true potency could be as low as 88% — potentially below the acceptable threshold. Labs that report MU on their COAs demonstrate a higher level of analytical rigor. Labs that report only bare numbers without uncertainty are omitting information that affects how results should be interpreted.
What It Is Not
Measurement uncertainty is not analytical error. Error implies a mistake. Uncertainty is an inherent property of all measurements — even perfectly performed analyses have uncertainty from equipment, reference standards, sample preparation, and environmental conditions. MU is also not a pass/fail criterion by itself. It is additional information that helps buyers and regulators interpret whether a result genuinely meets specifications.
Evidence and References
- standardISO/IEC 17025:2017 clause 7.6
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