Just took test - noticed something on my laboratory form

[Burnt Toast]

From the DHHS regulations:

Substituted Specimens

The HHS criteria for identifying substituted specimens are based on the physiological ranges for creatinine concentration and specific gravity value of normal human urine.


A laboratory will report a urine specimen as substituted when both the initial and confirmatory tests (i.e., tests on separate aliquots) document that:

- The creatinine concentration is less than 2 mg/dL, and
- The specific gravity is less than or equal to 1.0010 or greater than or equal to 1.0200


Source: Drug Testing: HHS MRO Manual (Effective November 1, 2004)

As long as the batch is unexpired (which in this case it is) and had been stored properly (ie; no exposure to direct sunlight), you have nothing to worry about.