A specimen-validity result describes the specimen’s condition, not simply whether drugs were detected. Terms such as dilute, invalid, adulterated, and substituted have defined meanings under particular programs and can lead to recollection, medical review, cancellation, or other action.
For other result types, visit Understanding Drug-Test Results.
What is specimen-validity testing?
Validity testing evaluates whether a specimen is consistent with expected biological characteristics and suitable for analysis. Urine programs may evaluate creatinine, specific gravity, pH, oxidizing substances, or other indicators. The exact tests and thresholds depend on the governing program.
Dilute specimens
A dilute urine specimen has lower concentration measures than expected under the program’s definition. It can result from high fluid intake, medical factors, collection timing, or other circumstances. Dilute does not automatically prove intentional manipulation.
A report may be negative dilute or, depending on the findings, positive with dilution information. Rules determine whether a negative dilute is accepted or recollected. Federal and DOT programs have specific procedures based on the reported validity values.
Invalid specimens
An invalid result means the laboratory could not obtain a valid positive, negative, adulterated, or substituted result under the applicable criteria. Possible causes include interference, unusual specimen characteristics, handling problems, or a condition without a straightforward category.
The MRO or program may investigate medical explanations and direct a recollection. An invalid result should not casually be relabeled as a positive.
Adulterated specimens
An adulterated specimen meets criteria indicating a substance or condition inconsistent with normal urine or capable of interfering with testing. Regulated programs define the laboratory and review procedures. The donor may have an opportunity to present a legitimate medical explanation, although qualifying explanations may be uncommon.
Substituted specimens
A substituted specimen meets defined creatinine and specific-gravity criteria inconsistent with normal human urine under the program. It is a validity classification, not merely an informal suspicion based on appearance.
Temperature and collection observations
Some urine collections include a temperature check shortly after collection. An out-of-range temperature can trigger an observed recollection under applicable rules, but the laboratory’s validity findings and the collection event are distinct. Collectors should document facts and follow procedure rather than diagnose the cause.
What happens next?
Possible outcomes include:
- acceptance of a negative dilute under the program;
- immediate or later recollection, sometimes under direct observation;
- MRO review of an invalid, adulterated, or substituted result;
- cancellation when a valid result cannot be obtained under the rules;
- split-specimen testing or another dispute procedure; or
- policy, employment, treatment, or legal consequences after final verification.
Health and safety
Do not consume excessive water or use additives in an attempt to change a result. Excessive water intake can cause dangerous electrolyte imbalance. Adding chemicals or providing a substitute specimen can create a separate reportable result and serious consequences.
Questions to ask
- Which exact validity category was reported?
- Was the drug result negative, positive, or cancelled?
- Which program definitions and thresholds applied?
- Is recollection required and must it be observed?
- Will an MRO consider medical information?
- Is split-specimen testing available, and what is the deadline?
Continue with The Specimen Collection Process and Retesting and Disputes.
Sources
- SAMHSA: HHS Guidelines and Federal Testing Forms
- U.S. Department of Transportation: 49 CFR Part 40
- DOT: Part 40 Questions and Answers
Last evidence review: October 29, 2026.