When given the choice, it can be overwhelming to decide on which kind of drug test to take. Each kind has its own benefits and drawbacks, depending on when you last got high and how often you get high in general.
Blood, urine, hair, and saliva are commonly used in workplace and DUI testing, while breathalyzer tests for weed are in the works. But do you know which you’d be most likely to pass?
Depending on your weight and how often you ingest, THC (or tetrahydrocannabinol, the active compound in cannabis) can stay in your system for up to 11 weeks.
If you’re pulled over for what could be a potential DUI, police officers can still make an arrest if you don’t breathalyze positive for alcohol. And if you refuse to take a drug test, you can lose your license for a year.
Blood tests can best detect recent use, measuring active THC in the blood stream. When you smoke weed, THC levels in the blood will peak rapidly to about 100 nanograms per milliliter in the blood plasma, before declining to less than 10 nanograms within an hour. For approximately the next eight hours, THC in the system will level out around one or two nanograms. For chronic users, it can remain detectable via blood test for the next few days.
Because blood tests are more invasive than other drug tests, they’re not very popular. Typically, they’re used by law enforcement when investigating accidents or DUIs.
It’s important to note, however, that though THC may be detectable in the blood for several hours after ingestion, its mere presence does not indicate impairment.
Urine tests, on the other hand, can detect cannabis for days or weeks after someone has used it — which still only reveals very little about impairment at the time when the drug test is administered. Urine tests don’t detect THC, which causes the psychoactive effects of cannabis, but rather identify the metabolite THC-COOH, which can remain in the body’s system for over a month. Heavy users might test positive for more than two months after using cannabis, while a single use can be detected for up to a week — it all depends on an individual’s habits.
The hair test goes back even further. It can detect repetitive cannabis use for up to 90 days, according to Barry Sample, Quest director of science and technology.
A hair test can detect as little as 1 picogram per milligram of the THC metabolite, which binds to hair follicles beneath the scalp 10 days before it even reaches the scalp’s surface. Since hair grows about half an inch every month, and since hair samples are taken an inch and a half from the scalp, the math adds up so that the sample can go back about three months. The kind of hair you have, however, can determine how effective the test might be. Grey hair can show up with false positives, while the test might be more sensitive for darker hair samples.
Saliva tests, also called mouth swab or spit tests, can only detect THC for up to several hours to a day within use. The only way to pass one of these tests is to stop smoking about two days before you get tested.
The last type of test to look out for is the weed breathalyzer. While it’s still in development, one such breathalyzer, developed by Hound Labs, can detect THC in parts per trillion. Best for roadside encounters with erratic drivers, the breathalyze would be ideal for catching DUI’s.
There isn’t, however, any substantive information yet what constitutes impairment. Merely being “under the influence” or having THC or a THC metabolite in the body’s system does not mean a person is impaired.
With that said, whether you smoke every once in a while, or every day, next time you’re given the option to pee in a cup or have a strand of hair plucked from your scalp, you’ll now have a better idea of what the results could be.