pH measurement is performed systematically on all urine specimens submitted for drug testing to detect certain attempts to cheat.
The normal pH of urine is between 4.6 and 8.0. Some individuals seek to mask the presence of illicit drugs in their specimen by adding substances capable of destroying the drugs that are present or of interfering with the testing techniques. Many of these products will cause a change in the specimen’s pH outside the normal range, which can be detected in the laboratory.
A urine pH below 4.5 or above 9.0 indicates a possible attempt to cheat by adding acidic or alkaline products. pH values below 3.0 or above 11.0 are inconsistent with human urine (adulterated or substituted specimen).