# LOQ

> The LOQ (limit of quantitation) is the lowest concentration a method can measure with acceptable accuracy and precision; below it a result is reported as <LOQ.

- Canonical: https://genetixbay.com/knowledge/glossary/loq.html
- Also written: limit of quantitation, limit of quantification, quantitation limit, reporting limit
- Glossary category: Lab testing · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

The limit of quantitation is the lowest amount of a compound a validated method can put a reliable number on. It sits above the [LOD](https://genetixbay.com/knowledge/glossary/lod.md), often around ten times the blank standard deviation. Between the LOD and the LOQ a lab can say "something is there" but not "how much".

## In practice

A potency [COA](https://genetixbay.com/knowledge/glossary/coa.md) might show [CBN](https://genetixbay.com/knowledge/glossary/cbn.md) "<LOQ" with an LOQ of 0.05% w/w: the lab thinks it's probably present, below 0.05%. When labs report totals, check how they treat <LOQ values: counting them as zero, as half the LOQ, or as the LOQ itself changes the sum slightly. For contaminants, an LOQ above the regulatory action limit would make the test useless; accredited methods are validated so the LOQ sits comfortably below the limit.

## Units and formula

Same units as the result. A common estimate is LOQ ≈ 10 × SD of the blank, divided by the calibration slope; labs confirm it by spiking samples at that level.

## Don't confuse with

- **LOD**: the lower "is it there at all" threshold.
- **ND**: [not detected](https://genetixbay.com/knowledge/glossary/non-detect.md), meaning below the LOD.

## Related terms

[LOD](https://genetixbay.com/knowledge/glossary/lod.md), [ND (non-detect)](https://genetixbay.com/knowledge/glossary/non-detect.md), [Measurement uncertainty](https://genetixbay.com/knowledge/glossary/measurement-uncertainty.md), [COA](https://genetixbay.com/knowledge/glossary/coa.md), [Potency testing](https://genetixbay.com/knowledge/glossary/potency-testing.md)

## Sources

1. Ellison SLR, Williams A (eds). 2012. Eurachem/CITAC Guide: Quantifying Uncertainty in Analytical Measurement, 3rd edition.
2. ISO/IEC 17025:2017. General requirements for the competence of testing and calibration laboratories. International Organization for Standardization, Geneva.