Dilution of Creatinine levels in urine

Dear Ask The Doctor: I don't understand a drug test sult that came back from my ex husband. It says his creatinine indicats diluted urine which may be caused by clinical plyuria or dilution of the specimen. Falso negatives may occur. His creatinine level was 2.1mmol he is 35, helathy and fit and app 80-85 kg at 5ft11. Can I please have this explained as I can't find anything on google that I understand?

Dear Donna:

Certainly, the result of the urine creatinine is doubtful. For a man his age a level between 6 and 17 mmol per day might be considered normal.

Since his level is very low, probable causes of polyuria might need to be ruled out as well as dilution of the specimen done on purpose. I would suggest him repeat the test. I hope I cleared your doubt.