In lab results, what does ND signify?

• A. Not Detected
• B. Not Data
• C. Not Documented
• D. Not Determined

Answer: (A)

Not Detected means the test did not find the substance at or above the method’s detection limit. In practice, this tells you that if the analyte is present, its amount is below what the instrument or assay can reliably measure for that sample and method. It’s not saying there is zero of the substance, just that it’s below the detectable threshold for that test.

This is different from data not being available, not being documented, or not determined, which would imply missing or unresolved information rather than a measurement result. In a lab report, an ND entry specifically communicates the detection outcome for that analyte under the chosen method. If you need a quantitative value, you’d use a more sensitive method or a report that states the limit of detection used.