The buying guide
What non-detect means on a protein powder test
Non-detect is an analytical result tied to a method and reporting limit. It should not be rewritten as a measured zero or a universal heavy-metal-free claim.
Keep three situations distinct
A blank cell means the information is missing. ND means the report uses a nondetect designation. A result written with a less-than sign supplies a bound. These entries carry different information and should remain distinct in your comparison notes.
To interpret ND numerically, request the report's definition and applicable detection or reporting limit. Do not borrow a limit from another laboratory, analyte, or document. Methods and reporting conventions can differ.
Compare only what the evidence supports
When comparing two reports, retain their original qualifiers and units beside any converted value. A lower stated limit can affect how an ND result is interpreted, so a table that replaces every ND with zero can hide useful differences.
Our calculator leaves ND as nonnumeric when no bound is available. It can convert an explicitly reported less-than value without removing the qualifier. Neither result proves the absence of every contaminant, identifies every future lot, or answers a personal health question.