# LOD

> The LOD (limit of detection) is the lowest amount of a compound a method can reliably tell apart from zero, but not necessarily measure accurately.

- Canonical: https://genetixbay.com/knowledge/glossary/lod.html
- Also written: limit of detection, detection limit, MDL, method detection 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 detection is the smallest concentration at which a method can say "this compound is present" with stated confidence. Below the LOD, the signal can't be separated from instrument noise and blank variation. It is often estimated as about three times the standard deviation of blank measurements, though methods differ.

## In practice

A [COA](https://genetixbay.com/knowledge/glossary/coa.md) might list myclobutanil with LOD 0.01 µg/g and result "[ND](https://genetixbay.com/knowledge/glossary/non-detect.md)". That means the lab saw nothing at or above 0.01 µg/g, not that the sample contains zero. A result between the LOD and the [LOQ](https://genetixbay.com/knowledge/glossary/loq.md) shows the compound is probably present but the number isn't reliable; many labs report those as "<LOQ" or "detected". LODs vary between labs and methods, so ND at one lab and a detection at another can both be honest.

## Units and formula

Same units as the result (% w/w, mg/g, µg/g, ppm, ppb). A common estimate is LOD ≈ 3 × SD of the blank, divided by the calibration slope.

## Don't confuse with

- **LOQ**: the higher threshold where the number becomes reliable.
- **Action limit**: the regulatory pass/fail level, usually well above the LOD.

## Related terms

[LOQ](https://genetixbay.com/knowledge/glossary/loq.md), [ND (non-detect)](https://genetixbay.com/knowledge/glossary/non-detect.md), [Measurement uncertainty](https://genetixbay.com/knowledge/glossary/measurement-uncertainty.md), [Pesticide panel](https://genetixbay.com/knowledge/glossary/pesticide-panel.md), [COA](https://genetixbay.com/knowledge/glossary/coa.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.