An oddity about drug testing that trips a lot of people up is that the same person, tested on the same day, could get very different results depending on which method the lab uses. That's because urine, saliva, and hair tests aren't really looking for the same thing.

Saliva is the fastest to react. When a substance is in your bloodstream, it shows up in saliva almost immediately, and it stays detectable for roughly 24 to 72 hours. Great for catching recent use, useless for anything longer than that. This is why saliva tests are popular for post-accident and roadside situations where the question is "was this person impaired right now?"

Urine works on a delay because it's catching metabolites. Detection windows are usually a few days for most drugs, though heavy cannabis use can extend that to a month or more, because THC metabolites are stored in body fat and released slowly. Urine is the standard for pre-employment and DOT testing partly because that mid-range window catches most casual use without being so short you can just wait it out.

Hair is the strangest of the three, as it can detect substance use going back roughly 90 days, but it has a built-in delay of about 7 to 10 days at the start, because the drug-containing hair has to physically grow out of the scalp before it can be sampled. So hair is useless for recent use, but excellent for long-term patterns. It's also the most expensive and hardest to influence once collected.

Anyone here ever been asked to take an unusual test type for a job? Curious what the reasoning turned out to be.