Cannabis users may be exposed to screening tests for various reasons. Generally, these tests are performed on biological fluids (saliva, sweat, urine, blood) or hair.
For example, for an alleged driving under the influence of drugs, police may perform a screening test through saliva or sweat. If in a subsequent review the THC is found in the blood in excess of the permitted level, the individual is considered absolutely unfit to drive. So a search for THC or its metabolites, particularly THC-COOH, is tested in the urine or hair.
Presence of THC in biological fluids and hair
Blood - THC can be detected for five to twelve hours in the blood after smoking a single cigarette. For regular users it's one or two days after the last usage. But the detectability of THC-COOH is sometimes possible after five days, even for a single use. Thatís why blood testing is most often used.
Urine (Urine Drug Test) - the detection time is even more variable than in blood. Extreme cases have been documented more than six weeks after the last taken, although the results may be negative for about one week after detection. Urine removes THC unaltered but especially the products of metabolism, primarily THC-COOH. Detection after single use varies between one and seven days, two to three weeks for a more regular users and it, of course, depends on many other factors.
Saliva (Saliva Drug Test) - Little THC passes from the blood in saliva, so the metabolites are weakly concentrated. If consumption is through capsules or even badly chewed biscuit, consumption becomes almost indistinguishable. Detection can vary between one and twenty four hours. The "screening tests" are often unreliable and THC cannot be proven
Sweat - As with saliva testing does not yield correct results. By cons, intensive research is to perfect them. But the main advantage is that such tests can be done easily without interference with privacy, on mere suspicion before being confirmed by a blood test.
Hair (Hair Drug Test) - THC and its metabolites can meet there, but at very low doses and very variable. The absorption may be due to sebum, sweat or ambient air. There is more THC and its metabolites in hair that is rich in pigment- black hair. But in blond, gray or white hair their amount is much less. Investigations showed the presence of THC or THC-COOH in 85% of hair daily users and nearly 52% of episodic consumers. Consumption once or twice a month does not show any trace.