A diluted sample usually indicates a decreased creatinine level in the urine most likely brought on by drinking excessive amounts of water. Diluted samples are often sent for further testing to determine toxin levels at much smaller increments than the initial tests.

An invalid sample is different than a diluted sample.

We are receiving a few reports lately that a sample has been determined to be invalid, meaning that the lab has run tests to check for human elements such as uric acid and found that the sample contained none.

Uric acid is a waste product produced by our bodies as we break down certain molecules and is released in our urine. If uric acid is created at a rate faster than we can expel it through urination then it crystallizes in our bodies and the crystals are then released through the urine which can be a sign of health problems.  These molecules, called purines, are naturally found in the food we eat. Meat, beans, oatmeal and fish are rich sources of purines. High levels of uric acid are generally associated with diseases such as diabetes, gout, and cardiovascular disease. High amounts of uric acid in the system may lead to kidney stones.

Testing for uric acid levels is generally reserved for medical testing and not strictly for drug testing.  Synthetic urine contains no uric acid.  When applying for a position that requires a physical a test for uric acid may be conducted.