[Code of Federal Regulations] [Title 49, Volume 1] [Revised as of October 1, 2005] From the U.S. Government Printing Office via GPO Access [CITE: 49CFR40.93] [Page 652-653] TITLE 49--TRANSPORTATION Subtitle A--Office of the Secretary of Transportation PART 40_PROCEDURES FOR TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS--Table of Contents Subpart F_Drug Testing Laboratories Sec. 40.93 What criteria do laboratories use to establish that a specimen is dilute or substituted? (a) As a laboratory, you must consider the primary specimen to be dilute when: (1) The creatinine concentration is greater than or equal to 2 mg/dL but less than 20 mg/dL, and (2) The specific gravity is greater than 1.0010 but less than 1.0030 on a single aliquot. (b) As a laboratory, you must consider the primary specimen to be substituted when the creatinine concentration is less than 2 mg/dL and the specific gravity is less than or equal to [[Page 653]] 1.0010 or greater than or equal to 1.0200 on both the initial and confirmatory creatinine tests and on both the initial and confirmatory specific gravity tests on two separate aliquots. [69 FR 64867, Nov. 9, 2004]