A urine drug test is the most common way of testing for drugs. This is because drugs last longer in urine (days or weeks) than they do in blood or saliva (hours). Urine drug tests are also easier to do and you can test for a wide range of drugs from one sample.
Drugs last longest in hair, typically for months, but not every drug can be tested in hair samples. Hair drug tests are also much more expensive to do.
Drug tests are usually done in 2 steps.
The first step is to screen the sample for many drugs. If this is negative, then no other tests are done and the test is reported as negative.
If the first drug test is positive, then a second,more specialised, drug test is done to find out if it is a true positive. This second drug test is then reported as positive and the drug that has been found and its amount is put in the report.
A small number of first drug tests will be FALSE positives. In this case, the second specialised drug test will prove that this is a wrong result. The final result will be reported as negative.
We do the following types of drug tests: