The drug testing cut-off level is one of the most important aspects when it comes to testing for drugs. This is the level or threshold which determines if the test is negative or positive.
We express the concentration of a drug in nanograms (ng) per milliliters (mL). This is usually abbreviated as ng/mL. A nanogram is a very small unit consisting of 1 billionth of a gram. 1mL is about 1/30 of a fluid ounce.
Deciding Drug Cut-Off Levels
When we look at drugs that are abused the cut-off levels are set to test at the lowest level that still keeps the integrity of the test you’re conducting. This testing window is optimized and it allows for the detection of the drug which is being screened for.
Drug Cut-Off Levels for Cannabis
The cut-off levels for this drug vary. It’s dependent upon the type of test that’s being used. Two common types of tests used in the workplace currently are saliva and urine drug testing. The saliva test has a lower cut-off than the urine type of test.
Urine Drug Test Cut-Off Levels for Cannabis
The active ingredient in cannabis that causes the high is THC. Urine tests, however, set out to screen for another chemical called THC-COOH. This metabolite is produced when THC is broken down in the liver. THC-COOH stays in the body much longer than THC.
The standard cutoff level for THC-COOH used by drug test manufacturers is 50 ng/mL. Less frequently some tests may test at 20 ng/mL and 100 ng/mL.
In the UK, 50 ng/ml is generally the standard drug test cut-off for cannabis. This is used in any workplace screening that involves a urine test. Our urine drug testing kits all use the 50 ng/ml cut-off. Our 5 drug, 7 drug and 12 drug test kits, multi- parameter drug test kits, and single drug testing kits all use the cut-off level too. The detection window for cannabis when using a urine drug test is 3 to 5 days from the last use of the drug.
Saliva Drug Test Cut-Off Levels for Cannabis
There’s a lower cut-off for saliva drug tests when compared to a urine drug test. There’s a lower window of detection with a saliva test which is about 24 hours. The saliva drug test is usually used in situations where recent drug use or impairment is under monitoring.
Drug Driving Test Cut-Off Levels for Cannabis
In March 2015, new drug driving legislation was introduced, making it illegal to drive a vehicle whilst under the influence of any of a list of 17 legal and illegal drugs. Cannabis is one of the drugs that is prohibited under the new rules and the cut-off level for the drug is very low. Delta-9-Tetrahydrocannabinol (cannabis and cannabinol) has a cut-off of 2µg/L
Police use a special device, often called a “drugalyser” to take a roadside saliva swab which will determine if a driver is or isn’t over the drug drive limit. South Yorkshire Police have posted this YouTube video which shows how a drug driving test works.