There are no hard and fast rules but rather guidelines as there are many factors that can come into consideration.

Drug TypeCut-off LevelApproximate Detection Time In Urine
Marijuana THC50ng/mL0-30 Days
Cocaine COC300ng/mL2-4 Days
Methamphetamine METH300ng/mL3-5 Days
Opiate OPI300ng/mL2-4 Days
Amphetamine AMP300ng/mL2-4 Days
Benzodiazepines BZO200ng/mL3-7 Days

The above chart gives approximate detection periods for each substance. The ranges depend on the amount of use, metabolic rate, body mass, age, overall health, drug tolerance, and urine pH.